Jewelry isn't expensive because it is scarce, [its expensive because people control its value very tightly][1].

The scenario you described is happening right now, [diamonds are able to be made on an industrial scale cheaply, easily and on huge scales][2]. Yet [that hasn't impacted the De Beers profit in the slightest][3].

**Because diamonds, *real diamonds* aren't made in a lab in an instant, they are made in the Earth over an eternity. So if you want your love to last eternity, instead of an instant, get a real diamond.**


In short answer: What kind of jewelry would be valuable in a world where anything can be produced? The kind with the best marketing that appeals to its handmade authenticness, not its soulless creation by a machine.

  [1]: https://en.wikipedia.org/wiki/De_Beers
  [2]: https://en.wikipedia.org/wiki/Diamond#Industrial-grade_diamonds
  [3]: http://www.bdlive.co.za/business/mining/2013/12/03/de-beers-takes-shine-off-synthetic-diamonds