Imagine an intergalactic society that has the following abilities\tech:

  • Warp drive allows trips between stars in days and galaxies in weeks.
  • Able to live in spaceships for long time without health issues.
  • Full control over millions of star systems spanning multiple galaxies.
  • Super cheap power due to effective use of antimatter (which they can produce easily and cheaply, so that is not the answer).
  • Fully automated manufacturing of just about anything, every household has a fabricator in it that you put in the needed minerals and get out pretty much whatever you want (as long as you aren't trying to fabricate restricted items like weapons of mass destruction).
  • Can grow any plant life and breed any animal life super effectively and cheaply.
  • living space is not an issue, it's as common for a middle class civilian there to buy a vacation planet as it is for one to buy a car in RL.

What they don't have is the following abilities:

  • Can't transform energy to materials.
  • Can't transform one material to another in any way that modern chemistry doesn't already know of (any known method to transform one material to another they can do super cheap no matter how expensive it is for us, if we don't currently have a way to make that transformation in our modern world they don't have that ability either).

As a result they have huge amount of mining ships strip mining the galaxy to deliver all the minerals they need to keep their civilization going, the galaxy being huge they aren't worried of that running out any time soon.

My question is what would be the most expensive material to buy in that society and why?

Please note that even if that mineral would cost a few space-pennies per tons it's fine so long as it costs more space-pennies than any other mineral.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Commented Mar 11, 2019 at 16:27

30 Answers 30


Moving away from a pure element (covered by other answers) to a material, something that has a special property.

Consider something that is made rare by the very presence of your intergalactic society. Let's suppose your warp drives give off low-levels of some kind of radiation, so any alloys destined for sensitive equipment need to be space-smelted in special batches. A real-world example of this kind of thing would be Low Background Steel.

Another commodity that your society presumably still values is time. So any material that needs to be aged would have a very high value. Wood that needs to dry for 20 years. Trees that take 200 years to grow (sure, you can genetically modify them to grow quicker, but it's not the same). The scales of a fish that only sheds them once a millennium.

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    $\begingroup$ <Hollywood Narrator Voice>In a world where they can make anything, the one thing they can’t have more of.. is time...</Hollywood Narrator Voice> $\endgroup$
    – Joe Bloggs
    Commented Mar 8, 2019 at 20:44
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    $\begingroup$ @JoeBloggs and trees $\endgroup$ Commented Mar 9, 2019 at 5:58
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    $\begingroup$ Except that actually you can produce more time using relativity $\endgroup$ Commented Mar 9, 2019 at 5:59
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    $\begingroup$ While using relativity to jump ahead 200 years for your bicentennial trees to mature is excellent from the perspective of personally seeing the fruits of your labour, it's rather less useful when you want those trees for your soirée next week. Non-relativistic time is still a resource this society can't just manufacture itself more of, only conserve through efficiency $\endgroup$
    – Pingcode
    Commented Mar 9, 2019 at 13:30
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    $\begingroup$ @Mindwin Locally, FTL is not the same as time travel - you can't travel into your own past, even if you can travel into your own light cone. Depending on the curvature of the universe, there are timelike curves into the past, but I don't think FTL implies time travel in every circumstance. $\endgroup$ Commented Mar 11, 2019 at 14:41

Why Things Are Valuable

Basic economic theory says that a thing will have a higher cost as its demand outpaces its supply. Note that this doesn't actually take rarity into account at all. Rare things are expensive because they have an inherently small supply, but you can also have a relatively common thing be expensive just by increasing the demand for it massively. Think about the early spice trade, and how lucrative that was despite spices being a renewable resource (plant).

Typically for the kind of galactic civilization you are talking about energy becomes a limiting factor, but your premise says that that is cheap and abundant so it's out. Instead let's look at another part of your premise, and use that to drum up some resource demand.

Go-Fast Juice

You cannot have a multi-galaxy spanning empire without the ability to get places quickly. Thus, your hyperdrives provide the perfect excuse for us to have a constant, high demand for a resource. All you have to do is say that that hyperdrives require massive amounts of energy(cheap) as well as some other physical material to work. This other material has to be something that cannot be artificially created with any technique that we know about now, but that is a much smaller handwave than the fact that it lets you travel across the galaxy in a week.

Any ship that uses a hyperdrive will need some amount of this resource, and if you make it so that it wears out over time then there will be a constant need for it. Without hyperdrives the whole galactic civilization grinds to a halt, so this resource will be the one of the most important things to have a supply of. Added together and you have the perfect recipe for an expensive material.

Handwavium Examples

Here are just a few quick ideas for what this material actually is, and why it is rare/expensive.

Crystal Handwavium: The crystal that lets your hyperdrive work can only be found in specific areas/conditions. It forms naturally over time, meaning the supply is also limited. The crystal structure is too complicated to easily replicate. (A breakthrough in artificial crystal making is a good way to shake up the setting later on)

Refined Handwavium: The engine of your hyperdrive needs to be made from a very specific alloy which requires lots of processing and refining of different base resources. While none of this is expensive by itself, in aggregate the amount of time and resources that go into each gram of alloy is enough to justify the high cost of the final result.

Rechargeable Handwavium: Your hyperdrive requires a massive influx of energy which would be unsafe to generate using antimatter alone. Instead, energy is stored in large, rechargeable batteries that can then be dumped all at once to provide the necessary spike. The battery itself is not that expensive, and neither is the energy that goes into it. In this case the cost is simply due to the time it takes to charge each battery. Each hyperdrive trip can use up weeks, months, or even years worth of energy to perform. There is a maximum charge rate that effectively makes it so that users are better off just selling empty batteries to a charging facility and buying a new battery for the next trip.

For each of the examples above, all you have to do is tweak whatever increases demand or decreases supply and you can change how expensive it is to whatever suits your needs. Make the crystal only come from a single planet, or each battery require year's worth of energy for even short trips, or the refined alloy decay at a rapid rate and in constant need of replacement. You are already giving this setting a cool hyperdrive system, you might as well make them pay for the privilege.

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    $\begingroup$ I love the name "handwavium" $\endgroup$
    – Azsgy
    Commented Mar 9, 2019 at 15:48
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    $\begingroup$ Dune, anyone? Your answer sounds a lot like you're describing the spice melange.. $\endgroup$ Commented Mar 10, 2019 at 13:58
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    $\begingroup$ Is handwavium more or less available than unobtanium? $\endgroup$ Commented Mar 11, 2019 at 18:37
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    $\begingroup$ @MichaelRichardson. The names would suggest that yes :) $\endgroup$ Commented Mar 11, 2019 at 21:42

Handmade items made by a famous artisan from a famous planet.

These items could be decorative (paintings, vases), utilitarian (glassware, pottery, handbag, shoes), or functional (instrument, book (signed and numbered).

Basically anything that takes personal effort to make will cost more simply because someone will have to put forth the effort rather than just ordering something up from the fabricator.

A similar issue would be a subscription to WoW or other MMO game from a famous company or personality.

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    $\begingroup$ The question is about materials only, not processed goods of any kind. $\endgroup$
    – cypher
    Commented Mar 8, 2019 at 17:01
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    $\begingroup$ Your question and descriptions state no such requirement. $\endgroup$ Commented Mar 8, 2019 at 17:05
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    $\begingroup$ "What would be the most expensive material to an intergalactic society?" - material by definition is not a processed good. $\endgroup$
    – cypher
    Commented Mar 8, 2019 at 17:08
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    $\begingroup$ @cypher Cotton cloth is both a material and a processed good. $\endgroup$
    – Yakk
    Commented Mar 8, 2019 at 19:18
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    $\begingroup$ “The WoW subscriptions must flow!” $\endgroup$ Commented Mar 11, 2019 at 10:33

All in all it depends on what materials they use the most of. If the galactic strip miners use more carbon than they produce then you can bet it will become expensive in very short order! However, if they’re pulling apart the galaxy as fast as I think they are: there’s one thing that I think would be of interest:


Lithium is incredibly useful. It is also (cosmologically speaking) quite rare. Stars that are good at making it are also good at destroying it within themselves (the so called lithium discrepancy), so the amount that’s hanging around in the universe today isn’t actually that dissimilar from the amount that was made in the first place (in the Big Bang).

Given its myriad uses and the fact that you can only expect it to get more scarce as time goes on and your race uses it up the smart super-corporation would buy all the Lithium possible (raising the price), then sell it back later as galactic stocks run low.

Invest in Lithicorp today!

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    $\begingroup$ @TylerS.Loeper: Exactly, which is why a forward-thinking company is going to play the long game and buy up all the resources that can be expected to run into supply issues over incredibly long timescales. Lithium fits the bill, plus it’s hella useful, so I’d expect demand for it to be quite high, come the end. $\endgroup$
    – Joe Bloggs
    Commented Mar 8, 2019 at 16:38
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    $\begingroup$ This is a great answer. Following your link I found the following instructive graph: en.wikipedia.org/wiki/File:SolarSystemAbundances.jpg So after Lithium, I guess the most useful/least abundant is.. Scandium? $\endgroup$
    – K. Morgan
    Commented Mar 8, 2019 at 16:48
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    $\begingroup$ @K.Morgan: I dunno. Beryllium is pretty handy for certain alloys, and you could theoretically burn through some of the heavier elements fast enough that their relative scarcity becomes a real problem, though in the long run you know you’ll get more, so.. $\endgroup$
    – Joe Bloggs
    Commented Mar 8, 2019 at 17:06
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    $\begingroup$ @Eyeballfrog: yeah, but I took the OP’s mention of mining and just assumed this society was still exploiting natural resources rather than rolling their own. If these guys are using fusion and fission then the answer is very definitely: ‘whatever you use most of relative to how hard it is to make’, and since we don’t fuse any materials on industrial scales (or forcibly decay any bar in nuclear power plants) I have no idea what those ratios would be. $\endgroup$
    – Joe Bloggs
    Commented Mar 8, 2019 at 20:40
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    $\begingroup$ Cue Scottie voice: "We need those (di)lithium crystals captain! I'm givin' her all she's got!" $\endgroup$ Commented Mar 8, 2019 at 21:08

Whatever costs the most to deliver to a client in the promised condition

Using a Nuclear Reactor or Particle Accelerator, it should be possible to synthetically create any element.

Given that any element can be made, we can then assume that there is (almost) zero difference in cost when it comes to making and acquiring materials. Most of an item's cost will come after this process. Therefore only secondary and tertiary factors can affect the cost. The most expensive material will thus be determined by:

Secondary and Tertiary factors:

  • Transportation Costs and or Handling Costs. If you need an unstable isotope that needs special equipment to be transported, or needs to be moved very fast or with some other special accommodation, the price of the material will be higher.

  • Supply and demand. In the end, as Joe Bloggs pointed out in his answer, this is the biggest determinant of cost. If you have a rare material that no one wants, it may be cheap. But a plentiful material that is always in short supply may be the most expensive. The most expensive resource will be what your civilization needs the most, but isn't supplied as much as is needed.

  • Cost of production and Regulation. This will likely be the same for most materials. However if special requirements must be met in order to qualify for production these will affect the cost; things like acquiring patents, government licenses, or passing other arbitrary obstacles. Finally the cost of labor, electricity, heavier metals requiring more power and atoms to make, and so on will influence the cost. However probably not as much as the other structural factors.

Some ideas for expensive materials:

  • Heavy metals with short half lives (transportation based costs).

  • Carbon, Oxygen, Silicon, or anything that might be needed constantly (demand based cost).

  • Patented Material-X, which can only be made by a single company by law. So the price can be extorted as much as the owner wants (Monopoly based cost).

Some great reading on the synthesis of elements, cited by Agrajag in the comments:

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    $\begingroup$ Note that some elements may be harder to create than others. Both purifying the material and producing it may be hard. I mean, stars already create elements this way, but some are far more rare than others due to how the process works. $\endgroup$
    – Yakk
    Commented Mar 8, 2019 at 19:19
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    $\begingroup$ Carbon oxygen and silicon are among the most abundant elements in the universe $\endgroup$
    – Gimelist
    Commented Mar 9, 2019 at 3:04
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    $\begingroup$ This may be true for small samples of material, but it might become prohibitively expensive for macroscopic quantities. A few atoms might be easy to make, but any useful amount takes a ridiculous amount of time and energy. $\endgroup$ Commented Mar 10, 2019 at 15:22
  • $\begingroup$ @BobTheAverage, The question states, "any known method to transform one material to another they can do super cheap no matter how expensive it is for us". $\endgroup$ Commented Mar 11, 2019 at 13:28
  • $\begingroup$ @TylerS.Loeper It also states that you can't transform energy into materials. Because of the ridiculous energy requirement of this process, you are pushing that boundary. The answer is looking for something they CAN'T do easily, so looking hard for reasons they can do it is not helpful. $\endgroup$ Commented Mar 11, 2019 at 15:36

Legally-regulated or illicit substances

Unless you count exotic phases of matter (e.g. quark-gluon condensate) to be "materials", then the most realistic expensive material would be one which the most powerful organizations of your galactic society actively attempt to prevent the proliferation of. This could include illicit substances such as drugs or regulated materials that could be used in the creation of weapons. Consider the situation today on Earth where substances like cocaine are not difficult to create, but go for a very high price. Gram for gram, other substances such as LSD can be even more expensive despite being possible to synthesize.

Imagine some terrorist releases an exceptionally deadly neurotoxin in an interstellar subway station that acts fast enough to kill people before rescue efforts have the opportunity to provide antidotes. Intergalactic media would be quick to vilify this terrorist organization and might even be instrumental in getting the neurotoxin itself or its precursors banned throughout the entire cluster. With multiple powerful governments utilizing extremely advanced technology to stem the spread of this illegal substance and hunt down those producing it, its market price could go way, way up.

Unique materials with sentimental value

Small pieces of laminated paper are extremely cheap to produce today, but that doesn't mean that extremely rare baseball cards don't go for literally millions of dollars in an auction. There is no reason why this wouldn't be the case for a future society where memorabilia left over by their heroes could be worth a fortune. How much do you think the plumbus used by the civil rights leader Shrimply Pibbles1 would be worth? Just because raw materials are cheap does not mean unique items need be.

Materials that can only exist in exotic environments

There is no place you can go to get quark-gluon plasma2 anymore. The surplus of quark soup began some 10-32 seconds after the big bang and ran out around 10-6 seconds (or one microsecond) afterwards, during the quark epoch. While quarks and gluons are common materials (you'll find it anywhere you find matter), the plasma state can only exist in environments with levels of energy on par with that of the early stages of the big bang itself. It cannot exist in a low-energy medium.

Generating this material today, while theoretically possible with sufficient energy, would be so difficult that the price would be ridiculous. Even if you had the substance, maintaining it in a state with enough energy to exceed the binding energy of hadrons and prevent it from hadronizating (spontaneously decaying into "normal" baryonic matter) would be remarkably difficult. After all, it only exists at trillions of kelvin. There is no known technology today to focus that amount of energy, given that even the heat from the center of a star is insufficient to form and maintain this substance. The technology and resources to do that, even in your society, may cost quite a bit, making this substance (and its maintenance) exceedingly expensive.


Since other questions have mostly not explored the meaning of "material", I proceed as follows:


Entry 2 of 2 definition 3b

noun: a performer's repertoire

I suggest that the most valuable material in the whole of the galaxy would be comedy.

Not only extremley popular (being among the most popular forms of entertainment today in America, The UK and much of the rest of the world), but it can be simultaneously entertaining and instructive, it lends itself to cultural critique, and as an audience participates in the mystique of the experience, they can experience a sense of community that the non-religious may not find elsewhere.

As a vehicle for social change:

Stand- up comedy is made unique by the fact that it encourages such a space, in which people can think critically about the outside space from within the safety of the liminal or littoral space.

The relationship between the audience and the comedian:

There is the element of conversation in a performance, in which the comedian delivers her material and the audience reacts, each adjusting and responding to the other accordingly. Then there is the balance of the aggression and awe which the audience feels towards the comedian, who confronts fearful things onstage, but in the process of doing so breaks social norms. This can be characterized as a meeting of the sacred and the blasphemous: the audience condones the stand-up stage as a sacred space, thus allowing the comic to behave blasphemously there. The audience members feel, to varying degrees, a combination of awe at watching the comedian take on frightening taboos, but also feel aggression as a result of the fact that it offends their social sensibilities.

But how does it relate to social change then?

there is a pedagogy which takes place in stand-up comedy. The act of experiencing a well-crafted joke couples entertainment with instruction in a unique way. Because it is not classified as educational or instructional, stand-up comedy has the potential to convey 57 messages that often cannot be voiced in other ways. And in being genuinely entertaining, it has the ability to reach those who are often not reached by other forms of instruction. The dialectical nature of stand-up comedy ensures that the best performances are those in which the humor is based in truth, making it an ideal tool for effectively critiquing unjust or oppressive situations

(The "57 messages" is, I believe a figurative expression of the bullshit that people put up with. The men in white coats are knocking at your skull.)

While referring to comedy, this may be the least funny answer. Irony.

For other refs please see BBC Comic Relief.

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    $\begingroup$ Entertainment, +1. You chose an interesting 'profession'; mine would've been 'the first'. $\endgroup$
    – Mazura
    Commented Mar 8, 2019 at 21:31


From Wikipedia:

Astatine is a radioactive chemical element with symbol At and atomic number 85. It is the rarest naturally occurring element in the Earth's crust, occurring only as the decay product of various heavier elements. All of astatine's isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours. A sample of the pure element has never been assembled, because any macroscopic specimen would be immediately vaporized by the heat of its own radioactivity.
[...] Astatine is likely to have a dark or lustrous appearance and may be a semiconductor or possibly a metal; [...]
[...] A visible piece of astatine would immediately vaporize itself because of the heat generated by its intense radioactivity. It remains to be seen if, with sufficient cooling, a macroscopic quantity of astatine could be deposited as a thin film. [...]
[...] Astatine is sometimes described as probably being a black solid [...], or as having a metallic appearance (if it is a metalloid or a metal). The melting and boiling points [...] are estimated to be 575 and 610 K (302 and 337 °C; 575 and 638 °F), respectively. [...] Astatine sublimes less readily than does iodine, having a lower vapor pressure. Even so, half of a given quantity of astatine will vaporize in approximately an hour if put on a clean glass surface at room temperature.

Emphasis mine

I think it could be a very valuable resource for rich people and entertainment for parties.

The richest people in the galaxy could use this resource as a new show to entertain guests during special events and parties. Imagine placing an astatine statue (or in another shape) in the middle of a room and show how this fine piece of art melt and evaporate over the time of an hour. Maybe, the party could finish when the last piece of the statue evaporate.

This resource would be extremely expensive since its extremely difficult to gather, and you must:

  1. Find the resource or "manufacture" it though polonium-2010 decay or bombard of Or 20983Bi with 42He.
  2. Harvest it.
  3. Refine it.
  4. Shape it to the piece of art or furniture you want.
  5. Deliver it with FTL ships.

Everything in less than 8.1 hours (astatine-210 half-life)!

I can imagine that the richest persons will have to make queue and reserve in anticipation for a find of this precious and exotic resource. Even more, during meetings, the waiting of these pieces of astatine to arrive at the party could be an event itself!

Parties will have to be made with a lot of planning near zones where miners think there could be astatine. Or, scientific should make an extremely fast FTL drive, able to supply the required celerity needed in this product.

Even more, there could be several types of pieces. Some astatine isotopes have half-lives of an hour, other minutes and others even seconds. Each one for a different kind of event!

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    $\begingroup$ Your astatine statue might be pretty to look at, but it would also give all your guests a nice healthy dosage of radiation in the process. No matter how rare it is, if it's not particularly useful for anything (and in fact seriously hazardous just to be near), then it's not all that valuable either... $\endgroup$ Commented Mar 8, 2019 at 21:14
  • $\begingroup$ @DarrelHoffman, with their level of technology I am quite sure radiation, wouldn't be a problem. Also, they could have a radiation shield (either sci-fi, like the FTL drive, maybe an anti-radiation glass, or use lead and a camera to see the statue). $\endgroup$
    – Ender Look
    Commented Mar 8, 2019 at 21:17
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    $\begingroup$ +1 for an answer actually based on science, without inventing fantasy elements. $\endgroup$
    – Tom
    Commented Mar 11, 2019 at 11:38
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    $\begingroup$ Forget the radioactivity, the guests will be turned into a wisp of rapidly-expanding plasma by the generated heat if that statue is large enough to see. Ok, that might (or might not) be an exaggeration, but the statue would definitely not hold any solid shape: "any macroscopic specimen would be immediately vaporized by the heat of its own radioactivity" $\endgroup$
    – zovits
    Commented Mar 11, 2019 at 12:34
  • $\begingroup$ @zovits That is why the statue will need very good refrigeration, with FTL technology and being the most expensive resource in the galaxy, I don't see a problem in cooling it with advanced technology. $\endgroup$
    – Ender Look
    Commented Mar 11, 2019 at 16:38


Thomas Malthus didn't know the half of it.

So, your intergalactic society can fabricate anything it wants. Since it can control antimatter, mass nucleosynthesis is a breeze. So the raw material is nucleons (protons and neutrons), which are the simplest, most stable examples of baryons -- three quarks bound by the strong nuclear force.

The thing is, economies survive by growing. More and more people/beings will need more and more stuff, and the raw materials for this stuff.

Baryons are a pretty inelastic supply -- they were all created right after the Big Bang. A dwindling supply, actually, because of all the baryons dissapearing down black holes all the time.

Eventually, your society will use up all the available baryonic matter in any particular volume of space to make up...people/beings, and their stuff. Recycling baryons from old stuff might buy time.

Bringing more from further out will cost more and more energy...eventually, you will hit peak baryon, where that cost is greater than what you get out of it.

Yes, the universe is big. It might even be infinite in extent. But that's even worse! You will inevitably run into another intergalactic civilization in exactly the same situation!

Here's a relevant YouTube video (Numberphile channel): https://youtu.be/lpj0E0a0mlU

  • $\begingroup$ literally everything is made of baryons, your answer might as well be "stuff" $\endgroup$
    – John
    Commented Apr 6, 2022 at 19:50
  • $\begingroup$ @John For one thing, only anout 5% of the Universe is baryons. Anyway, OP's conditions make "stuff" fungible, with baryons the basic unit. $\endgroup$
    – Spencer
    Commented Apr 6, 2022 at 22:22

Things that can only be found on a single planet, which means unique biological products.

Any mineral,or industrial product will occur on millions of worlds so they have little value., The only things unique to individual worlds are the lifeforms on those worlds. These can be divided into two categories products of individual intelligences and products of evolution.

Products of individual intelligences are works by famous persons or peoples, Irish whiskey is special because it is irish whiskey, even though people can have equivalent products they want the authentic ones. Alternatively you have products of single people or events, A Picasso or the car used in the film james bond, each of this is unique and a large part of their value is their uniqueness.

Products of evolution they things produced only by a single group of organisms, feathers are a rather complex structure unique to birds, it has an unique and unusual history that makes it unlikely to evolve independently anywhere. It is unlikely that you will find feathers on any other world. These of course can interact Milk may be unique to earth and because of that so may be cheese. An even more extreme version would be things like coffee of chocolate which are products of a single plant species, and one that is not that easy to grow.The more unique and specialized the environment needed for something the less likely the organism will be exported. Exporting organisms is also risky you never know what will become the next cane toad. Plants often have cooperating fungi which may become dangerous in new environments.

This will also come into play through interactions with other worlds, perhaps capsaicin is a stimulant for an alien biology, or perhaps serves as an antibiotic on some worlds. the interaction between alien biologics will be a whole industry, perhaps earth life has a different handiness of as alien B's world so molecules have a completely intuitive interaction. maybe earth food has flavor but no caloric value or maybe mustard is a narcotic.


Stealing a page from https://www.schlockmercenary.com/ -- post trans uranic elements.

Nuclear synthesis of elements is well within modern nuclear chemistry abilities; given a T3 civilization, mass synthesis of most convential elements should be possible for anything so rare that disassembling entire planets and stars doesn't generate enough of it.

But at the edge of current nuclear chemistry is the synthesis of post trans uranic elements in a hypothesized "island of stability".

An "island of stability" is a region where the proton/neutron shells in a nucleus are more stable than naive models would predict. If we posit that there is an island of extreme stability (not just fractions of a second, but fractions of an eon) in the post-trans-uranic elements, reaching them could be extremely expensive yet feasibly in a T3 civilization.

Nucleosynthesis in stars depends mostly on single-step absorbtion of He4 or other "light" nuclei followed by decay, then more He4 absorbtion. A fast decaying nucleus has little time to "double-absorb" a light nucleaus, so some regions of stable proton/neutron balance are mostly "out of reach".

Some elements are even generated through neutron-star neutron-star merger, like gold.

A hypothetical civilization capable of doing nucleosynthesis on scales more impressive than ramming two neutron stars together might be able to construct elements with useful properties that are otherwise not found in nature.

Of the civilizations technologies, only Warp Drive is beyond our current ken; everything else is just simple extrapolation of our civilization to more fine-grained control and higher energy budgets.

Warp Drive warps space itself. Manipulating near-singularity level gravity gradients to tear apart and merge nuclei could be an example of nucleosynthesis that nature could not duplicate; when it happens (in black hole mergers) it would end too quickly for stable nuclei to form, and any byproducts would cross the event horizon and be trapped inside the black hole.

In aforsaid https://www.schlockmercenary.com/ fiction, PTUs in any quantity are both made by industrial use of gravity generators and key in making gravity generators. To generate a significant amount of PTUs, you first need a significant amount of PTUs. With a slow enough exponential curve (imagine if 1 thousand units of PTUs allows you to generate 1 unit if PTUs per year) and the PTUs themselves being highly useful (if you want warp travel to be cheap without it, imagine if PTUs allow engines that enable warp travel that is 1000x faster), you'd have an extremely, extremely expensive material (suppose the energy output of an entire galaxy is sufficient to generate 1 unit of PTU per year, and 1 unit of PTU is enough to generate a fast-warp drive for a 100 tonne ship).

Suppose there is a factory galaxies. After a thousand years you have 1000 units of PTU, which if gathered up can produce a second unit of PTU per year (ie, every 1000 years, the amount of PTU doubles).

After 10,000 years you'll have 1000 units of PTU produced per year.

After 100,000 years you'll have 1 million units of PTU produced per year.

After 1 million years, you'll have 1 billion units of PTU produced per year.

At any point in this curve, PTUs can easily be the most valuable thing the civilization has; even with an output of 1 billion units/year, a multi-galaxy civilization will find that equipping every one with an unlimited number of starships with "fast" warp wouldn't be trivial. And that could easily be a good chunk of a million years in the future.


Unstable Reagents

Manufacture is, perhaps, a possibility; but one thing everyone seems to gloss over is that once manufactured, a material would need to remain stable for its use. I encourage you to consider materials like tungsten trifluoride, which is fully capable of continuing to burn in a vacuum and reacts with almost everything. (It's a better oxidizer than oxygen itself, and basically a real-life alkahest; you get it on your fingers, there's little to be done.) The very factor that makes them valuable would also make them extremely difficult to transport.

Another great example is the artificial noble gas, Oganesson. It's element 118, and the most radioactive material known to man. Whether there's a use to it has yet to be seen, as we've only produced it enough times to count on one hand. While your civilization may be able to produce it, it has a half-life of 0.66 ms (more or less), so transporting it would require a handwavium container that's turned up to 11.

  • $\begingroup$ For something to be valuable, it has to be useful. Og has too low of a half-life to be useful for anything. $\endgroup$
    – Gimelist
    Commented Mar 9, 2019 at 3:07
  • $\begingroup$ Depends on what you're using it for. We're talking about speculative fiction, after all. Besides, that is merely a single example. $\endgroup$ Commented Mar 9, 2019 at 4:00

Exotic Matter (Negative Mass) or just Unobtanium

You said you have FTL drives, but you didn't specify how they work (only said warp drive). They could use a special fuel to work, and since FTL is the most important thing in any galactic-size operation, this fuel would be the most expensive thing in the entire universe.

Just imagine being able to control the production of this special fuel, you could control entire empires with this unique resource. Everyone will be under your power, even more, you create and destroy with it (without FTL's fuel you can isolate an entire sector of the galaxy during thousands of years).

You could simply use unobtanium to feed your hyperdrives. Or if you like hard science, exotic matter:

Exotic mass has been considered a colloquial term for matters such as dark matter, negative mass, or complex mass

For being exactly, you could use a certain kind of exotic mass: negative mass:

Negative mass would possess some strange properties, such as accelerating in the direction opposite of applied force. Despite being inconsistent with the expected behavior of "normal" matter, negative mass is mathematically consistent and introduces no violation of conservation of momentum or energy. It is used in certain speculative theories, such as on the construction of artificial wormholes and the Alcubierre drive. The closest known real representative of such exotic matter is the region of pseudo-negative-pressure density produced by the Casimir effect.

That allows you to use both Alcubierre drives (warp drives) or traversable wormholes.

Allow me to perform a brief introduction to both FTL drives:

Alcubierre drive

You are already using it so I think you already know something about it. Anyway, I'll write about it.

I've already explained it in this answer, but I'll add about the exotic matter:

The sci-fi warp drive or the currently theorized Alcubierre drive use the principle of space-time distortion (primarily based on gravitational distortions).

enter image description here

Rather than exceeding the speed of light within a local reference frame, a spacecraft would traverse distances by contracting space in front of it and expanding space behind it, resulting in effective faster-than-light travel. Objects cannot accelerate to the speed of light within normal spacetime; instead, the Alcubierre drive shifts space around an object so that the object would arrive at its destination faster than light would in normal space without breaking any physical laws.

Basically, you contract (bench downwards in 2D) space in front of you (so you could travel a "smaller" distance towards your destination) while you expand (bench upwards in 2D) the space behind you (enlarging the distance towards your start point). Contract space is quite "easy", you just need a lot of mass or a huge amount of energy (due mass-energy equivalence). Instead, expanding space require negative mass, and thus exotic matter.

As a minor failure the Alcubierre drive has some limitations:

  • Mass-energy requiriment: A lot of negative mass, thought new speculations think it isn't so much, and so it's possible. Anyway, you must shrink it into a wall really thin, something a few orders of magnitude bigger than Planck constant, that is, really small.
  • Placement of matter: Some theories require pre-made (subluminical made) high lines, routes or railroads to use the drive. Otherwise, you will need tachyonic matter, which scientists aren't very optimist about its existence.
  • Survivability inside the bubble: During the FTL travel, since you are moving faster than light and in a space warped sphere, your ship's sensors get blinded, so you can't see if you are going to crash with something. Also, the hawking raditaion produced by the bubble (which I don't know how it is produced) may kill, smelt or "cook" for being exactly everything inside it.
  • Damaging effect on destination: When the ship decelerates from FTL, the particles (like hydrogen) that the bubble gathered during the travel would be released with so much energy that they will blueshift into deadly radiation, effectively annihilating any life in front of the ship. Better not point towards Earth.
  • Casuality violation: Like any FTL drive, the casuality could be violated due time travels.

It's your work see how to fix, avoid or just ignore the side-effects of the FTL travel.

Traversable Wormholes

If you would like to add portals, you could use wormholes.

You could watch this fancy and animated Kurzgesagt – In a Nutshell video about wormholes. Basically, to make a wormhole you need a massive amount of mass, enough to bench spacetime itself and tear it making "holes" on it. In order to do that, you need to compress a lot of mass into a single point.

After breaking the spacetime on that place a wormhole between to point of space will appear. That was the easiest part.

Now the problem is maintaining it. Due to the gravitation collapse of matter, the "tunnel" between that two points of space will suddenly close, at the same time both "mouths" of the wormhole turn into black holes. That is the difficult part, in order to move through a black hole, we need to surpass four things:

  • Spaghettification: or noodle effect, the gravity of the wormhole/black hole increases so quickly as you came close that the gravity between two different parts of your body/ship isn't the same, and so you tear apart, turning into "spaghetti".
  • Time dilatation: as you came close to the centre or singularity, the gravity increases and so time dilate, effectively taking infinite time to move through a wormhole.
  • Event of horizon: the gravity is so strong, that after cross this line or horizon, you are no longer able to turn back. So, once you enter into a wormhole, you can no longer escape from any of both sides.
  • Singularity: the gravity on this point (note that I said point and not a sphere) is infinite, the "tunnel" collapse, as time does and everything we know.

Luckily, all those things can be fixed with the same thing... you guess it! Exotic matter! If exotic matter (negative matter) works as scientists want to believe it will produce anti-gravity.

Mass object bench space "downwards" (on a 2D sheet) creating gravity and pulling objects near. Negative mass objects bench space "upwards" creating anti-gravity and pushing objects away. With enough amount of exotic matter and luck, we could "inject" it to a wormhole avoiding it to collapse due to gravity into a black hole, and thus avoiding any singularity, even of horizon, infinite time dilatation or, if the wormhole is enough big, even Spaghettification.

By the way, if you use any other type of FTL drive, like a jump drive, hyperdrive or hyperline, you could just use unobtanium.

PD: I am not physic, I might be forgetting/misleading/misunderstanding something.



According to your stated technologies, I will guess that Nanomaterials will be the most expensive materials in this society that you describe, depending on the technology that exists in your hypothetical fabricator technology. The structures can be complex, and thus will take complex and powerful fabricators, and will have a production bottleneck. These types of structures are desired for their fantastic properties.

As of 2017, endohedral fullerenes, a nanostructure formed by trapping a larger atom within a carbon fullerene shell, were the second most expensive material on our planet.

Nanomaterials can have many fantastic physical properties. Carbon nanotubes or sheets are expected to have tremendous physical strength. We have recently developed transparent ceramics using nanoscale techniques. Among these, Aluminum Oxynitride, can be used to make bulletproof windows.

If you don't like that, moving down the list of our current most expensive materials, we find Californium. I wouldn't use that, but would move on down the periodic table, to something within the (hypothetical) island of stability and create a new element. This new element would be incredibly dense, and likely very hard, and would replace things for which we currently use depleted uranium: Armor, Ammunition, and as a tamper in Nuclear Weapons

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    $\begingroup$ The problem with this is that if something becomes valuable, cheaper ways to create it are likely to be found. (Ordinary fullerenes, for example, have dropped in price by a factor of more than a million; over the past century, a similar drop in the cost of laboratory-grade silicon took place.) $\endgroup$
    – Mark
    Commented Mar 8, 2019 at 23:06
  • $\begingroup$ @Mark. True. It is just just a suggestion, take from it what you will $\endgroup$
    – Mike Vonn
    Commented Mar 9, 2019 at 20:43

If fabrication of anything is cheap, but transmutation of elements is not allowed, then the logical answer is "Material containing chemical elements with the highest demand/supply ratio".

It is not necessarily the rarest of the elements - if this intergalactic society has no use for it, it would be relatively cheap.

But I think it is very unlikely that a Kardashev III civilization would have no ability to transmute elements on large scale. Transmuted elements may have a higher cost (like desalinated water is more expensive than natural freshwater), but they should be widely available.


I am not certain about how you define materials, but one answer is information. A detailed map of this inter galactic civilization would be invaluable. Also, communications technology from the hardware to the "phone numbers" of people would also be priceless. In a civilization where everything you need is cheap, trade secrets would be one of the few commodities left. Another answer is copyrighted forms of entertainment. An The intergalactic number one hit is sure to be in high demand.


The society you describe will likely be able to manufacture any material item at will, in amounts sufficient to fulfill demand. Any valuable property therefore must be essentially immaterial, like information or art.

One nice example is Charles Stross' Singularity Sky. A nomadic culture called The Festival (!) visits Rochard's world, and they drop mobile phones from orbit. If picked up, they would say "Entertain us, and we will give you what you want." The Festival is in perpetual search for entertaining stories.

Of course the immaterial value can be imbued in a material item, like some object with artistic value. But it is not the material that is valuable, it is a unique, hard-to-reproduce immaterial property which even a faithful reproduction would not possess. A trivial example would be that the Mona Lisa would probably be very valuable even in that society capable of perfect reproduction. (Which makes me think that one would need strong cryptography to tag originals.)


Original Content

if your telling me that the base building blocks of everything is cheap and so is the manipulation and transportation of these building blocks then I would what would be the most expensive material out there.

I'd say a used canvas.

Once the barrier to creating objects has been reduced to only be limited by the creators skill and creativity. I believe that the value of objects will then be evaluated on creators skills.

It could be quickly seen that original content now becomes the most lucrative and expensive material.

With a civilization scope as large as yours (intergalactic), imagine how much an original painting from a painter known by 1 out of every 100,000 people would go for. Even today based on who painted and whos owned them paintings can sell for much more than sum of their materials.

It's not a far stretch to see that if wealth would remain steady and that the price of all materials go down that the value of artistic content would go up. "I can now afford to buy any car I want... does it come in radioactive green with a hand painted portrait of myself on the hood?"


I think the other Answers cover it quite well, this question stuck with me and I think I found something interesting:


Not slaves for the dirty work as there are machines for that. Skills that can't be replicated by machines / AI and future technology. Maybe even just the skillset to keep said technology going. As things get more and more and more specialized and complicated you need the right people to do that. Sourcing them would be quite expensive, complicated and depending on the skill, quite specific and only required on rare occasions.

Those skillslaves would be kept in cryostasis (or something familiar), in a form-factor box with enough energy to keep them stored for aeons (some future battery/mini-generator).

It keeps them from dying / ageing and losing interest.

This principle could either be an illegal practice where skilled people are abducted and traded. Someone gruesome could even specifically alter whole planets, nurturing talent in the population to grab as many people as possible. It could be a legal and common practice with volunteers. It could be something in between, I think all cases can make for quite some nice ideas/stories.

One skill that I can think of would be programming languages (get that legacy support, just freeze them devs)



Not because of the cost to make one. They will be actually be quite the cheapest thing to acquire, since they are self-replicating.

They have an expensive cost of ownership, though, because the way they replicate is by turning everything else into more strangelets, by contact, katamari style.

In principle, making even just one may spell doom to everyone and everything in the multiverses if left unchecked. The only way to make sure you will never lose your post-singularity empire to the nothingness is to have no light-cone interactions with the strangelets.


No material would be unusually expensive...

You've framed your question so that every material (manufactured or raw), or animal, or plant is easy to obtain, and people routinely buy entire planets...

You've even ruled out a fundamentally "cheap" item becoming ultra expensive (like Tulip Mania in Holland) since literally any item can be easily made/grown/bought. Even hand-made artwork would likely be easily duplicated in your "household fabricator."

But you do give a hint at what's not so easy to obtain:

  • Fully automated manufacturing of just about anything, every household has a fabricator in it that you put in the needed minerals and get out pretty much whatever you want (that isn't restricted like weapons of mass destruction).

I'm assuming weapons are restricted since killing people is frowned upon. So you're only leaving yourself with two possible things that would be hard to obtain, or limited in any way:

People, as in an army, or skilled workforce.

Or the more gruesome part two:

The (mass) destruction of people


In a post-scarcity world where everything is fully automated and any item is just a replicator or near-magical 3D printer away, I think that genuinely handcrafted products or vintage foods/drinks will be the SECOND MOST expensive of all, due to the sheer fact that the mastery of the skills required would have had to endure throughout the ages where there was contact with the galactic empire at large.

Especially when they were made at great (mortal) cost to the producer, which a perfect replica could have been made in an instant, but it wouldn't have quite the backstory, as stories to tell about authentic experiences are the real currency of a post-scarcity galactic civilization and THE MOST expensive.

Therefor, I wouldn't be at all surprised if some fancy immor(t)al alien being gifted a bunch of apes with some extra genes about a million years ago, just to have us create a nice logo for our global government once we reach global peace and then stealing it for his nanite-infused cellular rejuvenation potion named "Time's Unity" that he sells on the intergalactic market, leaving us to rot here in this hyperlane-less and warp-incapable pothole of space called 'Sol', while he scoots off at sublight speed, not giving a f***, being immortal.

This all relies on the fact that we as a species don't find enlightment in inner space (or cyberspace) and thus shutting ourselves off from the whole of reality in a simulation of our own, capable by ever increasing computational powers of outrunning the heat death of the universe by simulating more time in less actual time. In that case you don't talk about expensive; just 'hard to aquire' materials.



Just as humans value certain pets and are willing to pay large sums of money for them, aliens value humans despite them being such simple unintelligent creatures. While aliens are quite adept at breeding simpler animals, they've been unable to breed humans (despite many failed reproductive experiments on abducted humans) so need to rely on abductions to obtain them. Since this is technically prohibited by intergalactic law, it makes humans extremely expensive to obtain.

Beyond simple companionship, some humans are trainable enough to help out with menial tasks in alien households and some are even trained in jobs -- the aliens have a poor sense of smell (by human standards), so humans can be trained to use their acute sense of smell for some tasks. Other humans are prized for their appearance alone, and are entered into competitions to be judged on which ones best meet the breed standards.


The same things that are expensive now, because they are done the old fashioned way

Organic Food - People today are quite willing to pay a premium for organic food despite questionable evidence that it's much better for you.

Mined Diamonds - People pay a HUGE premium for diamonds mined from the ground, even though even the experts say they'll never be able to see the difference.

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    $\begingroup$ Or anything else where a company like DeBeers uses their monopoly plus clever advertising to artificially crank up the price. $\endgroup$
    – WGroleau
    Commented Mar 8, 2019 at 23:02
  • $\begingroup$ Many people prefer organic foods not for the supposed health benefits, but because they dislike the unethical treatment of animals and environmental damage caused by mass-market food. $\endgroup$
    – forest
    Commented Mar 10, 2019 at 8:23
  • $\begingroup$ Mined Diamonds can only remain expensive if DeBeers' diamond propaganda still holds sway over the minds of people and if they can somehow expand their cartel to include the entire universe. They're losing their grip even here on Earth! $\endgroup$
    – elemtilas
    Commented Mar 11, 2019 at 15:53

I am not sure a materiel will have much value at all in this kind of super-affluent society, with the whole universe of stuff available.

I think what will have value is:

  • A person's time

  • A sense of purpose and worthwhile work.

With all physical and material needs essentially unlimited and virtually free, it means people do not really have to work / sell their time.

This means getting someones time and personal service is a big deal.

On the flip side not much reason / need to do anything, so little purpose in life. For humans this seems to lead to a lot of problems - we (mostly) want to be part of and contribute to society, to do meaningful and valuable work.

This means that the opportunity of doing something important and worthwhile will become a valuable commodity.

Maybe we can combine them and say that the opportunity of performing an important personal service for someone is a valued commodity? That the chance to teach young children will be something people value highly?

  • $\begingroup$ If we're opening it up to non-stuff, I'd be tempted to add "trust" to your list. $\endgroup$ Commented Mar 9, 2019 at 17:25
  • $\begingroup$ I'm pretty sure none of those count as materials... $\endgroup$
    – forest
    Commented Mar 10, 2019 at 8:22


The forgotten dimensions. What with squillions of galaxies and gezillions of planets to explore, one simply does not have the time to explore even a repentillionth of them.

The human body has is designed with a scheme of planned obsolescence in mind. (This is because the Designer has other Plans for people than merely allowing them to wander the multiverse forever.) We can only replace broken down bits so many times. Things just wear down and ... die.

Given this framework, time itself becomes the single most valuable element in this universe. Either because no matter how technologically advanced your society is, sooner or later its stars will die and its very matter will decay; or else because no matter the scientific and medical advances, the individual will sooner or later die.


I didn’t see anyone mention ancient articfacts, possibly from extinct alien species. I could imagine some kind of new religion or government that still taxes resources heavily to collect power and influence, not really material but sill an expense. Perhaps you can’t trade with others without paying your tithe, or you become an enemy of the state without paying taxes.


Generally, Value Comes from Mass, not Composition

Can't transform one material to another in any way that modern chemistry doesn't already know of (any known method to transform one material to another they can do super cheap no matter how expensive it is for us, if we don't currently have a way to make that transformation in our modern world they don't have that ability either).

Since we already understand the principles of fusion, fission, chemistry, and nanostructures there is no element or compound that this civilization can't easily synthesize from other base elements. If you need Lithium or Gold or Platinum, you could just fuse some common lighter elements together to make it. If you need to create a terraforming organism just scoop up some dirt, differentiate the atoms through nuclear processes and string together some organic molecules until you have your specialized bacteria, easy peasy!

As such, the value of materials would just come down to mass rather than composition with two exceptions:

Whatever is Illegal

In a world where I can just make whatever I want, Governments will step in for the protection of the commonwealth to prevent me from making things that are considered too dangerous. While commercial fabricators could physically build anything, they would have safeguards to make sure I don't decided to violate intergalactic civil code 142.13a and build myself a Nova Bomb. Since the materials needed to make a star destroying weapon are pretty unique, I would need to acquire a specially unlocked fabricator to make them, thus pushing up the value of such materials.

Whatever is Proprietary

Being able to make something, and knowing how to do it are two different things. If I had the chemical formula for some unobtainium, my fabricator could make it, but since U-Corp has exclusive knowledge or rights to how it is made, I'd have to buy it from them at a marked up cost.


While the most expensive objects are going to be unique "value added goods" original art works and the like, the most expensive stable elements are going to those that are universally rare and useful in building spaceships and habitats etc..., Niobium & Rhenium for high temperature alloys, Tungsten and Titanium for high strength alloys, Indium for touch screens, Gold and Platinum as efficient conductors.


Not sure if it's still in scope of the question, but in such post-scarcity economy, most valuable items will certainly not be any material stuff. We already have "unicorn" corporations worth billions purely due to intellectual property and also the purely virtual Bitcoin blockchain technology.

On galactic civilization scale, this would amount to gathering stellar-mass-amounts of energy from, say, infall of material to galaxy's central black hole and using that energy for computation. That computation will foster virtual wealth of astronomical (pun intended) value, worth more than galaxy's manufactured materials.


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