As a few others have pointed out, your assertion if insanely expensive may not be the case.
To make this more clear as in answering your question more literally, the initial business's I list here require few people and have high-value profits. This is based on revising the one and done OR disposable approach we currently have. So a few people, initially maintained by Earth Resources have to provide cheaper solutions to existing problems we have. That is a formula for immediate profit. There are a lot of these things and that means a lot of jobs in space, just the cleaning up part and then add on the repair and refueling. This phase basically pays for the next phase the colonization and industrialization of the Moon. The people doing the initial jobs need someplace to go and Earth is expensive, the moon is cheap. The money flows.
Ways to be profitable.
The ability to refuel and repair existing space assets. What would one pay to be able to repair and upgrade Kepler, Hubble, etc?
The ability to cheaply build and implement new assets. How much would one pay to have new telescopes, satellites, etc; build in space then moved to the position?
The ability to provide Low Earth Orbit Habitats and provision them. How much would one pay to have large-scale habitats build in space and moved to low earth orbit, supply food and water grown by the Lunar Colony?
The ability to mitigate space hazards in Earth Space. How much would one pay to clean up the debris orbiting the Earth, to capture and utilize the Near Earth Orbit objects?
The ability to build, maintain and operate power sources for Earth. How much would one pay for the ability to build, maintain and operate a series of Solar Mirrors to provide clean cheap power to Earth ... as just one such method, X-Ray lasers and others would work as well.
The ability to Build and Launch exploration vehicles. How much does one pay to do this from Earth vs from an established Lunar Colony with infrastructure?
The list is rather long on ways to make money / be profitable in space.
We just need to start thinking like a Space-faring species, rather than a Planetary Species.
And what value would one put on being able to Reboot Humanity in the event of some self-inflicted devastation or some devastation from an external source? Just how much is that worth .....
To Expand ....
This is not about choosing Robots OR Humans. The state of the art in Robotic AI is not going to replace the flexibility, adaptability, or creativeness of Humans any time soon. So the relationship between Humans and Robots is cooperative existence. The number of Humans starts small and grows as the Job Opening / opportunities are created. Aside from the imperative of being profitable, the next greatest imperative is increasing Human presence. I want to see Blue Origin's goal of Millions of Humans working and living in Space to be a reality.
Phase 1 “We need to start somewhere”
So a few good people …..
For 40+ Years we have spent a lot of money doing the same things. There is an opportunity now to do something … very differently. SpaceX, Blue Origin, and others are providing the means for things to change. Not directly at this time, but indirectly. Right now Boeing, SpaceX, and others are providing for transfer vehicles from Earth to the ISS and back.
What would these companies love more than anything else right now? New customers doing new things. Also known as growth. For new customers, as in Humans in space … remember the opportunity to change ….
We have two very distinct and well-documented problems.
Japan has attempted to address one of them. We have a highly polluted space where a lot of our assets orbit. This needs to be cleaned up.
Japan’s current plan is to burn it up by reentry. BUT is that really the most economical way to do this? A lot of money was spent on getting it up there.
Is all of it really of no value? Why can’t we take it and use the Sun, as in a Solar Furnace to process it to a reusable form? I mean that is mass that has already been paid for to get it up there. Ok, let's assume I can do this and am building a stockpile of Gold, Silver, Platinum, Copper, etc. It will obviously have some value and would be rather easy to return to Earth for sale. BUT its mass has already been paid for to get to space. Well, now we have resources that can be used in the 3rd phase.
Phase 2 “I can repair, upgrade and refuel your Satellites”
So a lot more good people …….
Being in space and time on my hands, I can go to your Space Assets and do diagnostics, preventive maintenance, repairs, refuel, upgrades … you name it we will quote it and I am quite sure it will be significantly cheaper and significantly faster than you building a brand new one, insurance vs loss at launch, potentials for dysfunction etc.
We will be there, we will guarantee our work. Need that Satellite moved to a new orbit? We will quote that. Have a set of experiments you want to run? We will quote that.
Phase 3 “We can build it cheaper and faster in Space”
So a whole lot more people …...
Being in space and having the time, materials and facilities (see phase 1 and phase 2).
We can build your Satellite in space for you and deliver it to the desired orbit. We guarantee the price will be significantly cheaper than for you to build it on Earth and Launch it, with all of the attendant risk’s for failure. Remember we guarantee our work. It is even feasible we can build you two for the price of one, with the second being a backup/redundancy to the first one so you will not experience downtime, during our maintenance/upgrades.
What does all of this achieve?
For SpaceX, Blue Origin, Boeing etc. they now have a customer that is NOT politically fickle or driven. They have regular schedules to deliver food, water, and customer-supplied parts, in greater quantities than currently available to them.
For 3D Printers looking for a need to fill. Well with the accumulated resources and more economical deliveries from Earth based on competition and increased frequencies, it will become more economical for us to fabricate the parts in space than to have them built and launched from Earth.
We have learned how to Live and Work in Space and established a Space Population.
We need to be independant of Earth Resources.
Well, now then SpaceX, Blue Origin, Boeing etc have had time to see this coming. We need to become independant from Earth Resources. The thing we will need most are Space Transfer Vehicles. The ability to move around from point x to point y. The ability to move mass from point x to point y. They should be able to supply these vehicles and if they do not then we can supply them ourselves.
So the next phase Colonize the Moon.
Phase 4
Very little change in the number of Humans ...
Identify the easy picking resource of the Moon, focus on Water and Lava Tubes suitable for Human Habitation. Secondary any and all other resources that provide a source for materials currently supplied by Earth.
Phase 5.a
Very little change in the number of Humans ...
Select a Lava Tube for Habitation. Seal it, pressurize it, establish a power supply, establish a water source, both at the habitat and the source. Bad habits are hard to break, so we must keep this in mind. Use the water and other resources to establish a viable atmosphere. Establish a Life Cycle system. One might look at current Fish Farms. The ideal system will at a minimum provide food, filter the water, and prep waste for use in more traditional farm products. Ideally, in the end, it can do recycling of the atmosphere (plants … whatever).
Phase 5.b
Very little change in the number of Humans ...
Establish manufacturing systems and supplies. This means all the equipment and resources to produce the things used in Phase 1 through Phase 3 and the Space Transfer Vehicles.
Phase 5.c
Very little change in the number of Humans ...
It is imperative that any bad habits as using the Water etc for things that have very little to nothing to do with supporting Life need to be ended. I will go so far as to say creating a Space Vehicle that can be used to scoop the upper atmosphere of Earth (later the other planets/moons) for required gas’s. The focus needs to be on how to produce these gases from existing resources, other than water.
At the conclusion of Phase 5 we will have a model of how to Live, Work and be self sufficient on the Moon. This model can be used by any group to expand the Human Population on the Moon.
Phase 6
So a Human Civilization an explosion in the numbers of Humans in Space ……
Go Crazy
Build Survey Ships capable of building a data repository of the objects in OUR Solar System … all the way out to the Heliosheath / Heliopause.
Build Colonization Ships to be used to 1 shot colonize planets, moons, asteroids.
Build reservoirs of Water, from Comets … whatever.
Transition Humans to a Space-faring Species from a Planetary Species shall continue.