Suppose I own a piece-of-art and a copy. I swap molecules between them gradually, until the original no longer has any of its original molecules, and the copy has them all.

Which is the piece-of-art?

The art world probably has bizarre ideologies because they serve as investments and status symbols to elite patrons/customers. (And while the artist lives, they'd like to get paid. But our world isn't dominated by artists, so their subsistence isn't considered as important.)