I think, and I am not an expert by far, that this just shows what the market value of those art pieces are when removed from their context. You won't pay more than $30-60 for it unless you are told otherwise by someone of authority - an art critic or a market of affluent and competing buyers motivated by various reasons. There is also the fact that he did it in NY, where $60 is acceptable to many buyers. The sales would have been diffirent in rural Alabama or New Delhi.
