Mostly when people buy art, they're buying provenance, proof that a celebrity artist in history touched this particular object.
Forgers have gotten incredibly sophisticated, finding ways to duplicate the texture of historical paints and style of brush strokes of masters.
I think we'd do a lot of good for the world by commissioning as indistinguishable fakes as possible for all famous works, putting them in a room where the originals are all shuffled in, then sending them out into the world so any museum or private collector can have one, with some chance it's actually the real thing, but mostly the value would collapse to however sublime it is to actually look at the work.