You're not just buying "a piece of art" though. If that was the case, duplicates/prints/casts/reproductions or whatever would be worth a substantial portion of

You're not just buying "a piece of art" though. If that was the case, duplicates/prints/casts/reproductions or whatever would be worth a substantial portion of the original, relative to their true-ness. The value in owning art isn't the physical object. The value comes from how owning that specific physical object means you "own" that art, whatever that means. I don't really understand why anyone would care about that either, but people clearly do. And even if you disagree with that point, the other points about not owning copyright, lack of intrinsic value and using art for money laundering definitely apply to real art too.