Performance art
https://www.nytimes.com/2018/10/06/arts/design/uk-banksy-painting-sothebys.html
Art for art's sake: this was Banksy's masterpiece. But the art market, like all markets, is already showing signs of evolution and adjustment. Don't feel too bad for the purchaser, he can obviously afford it. Besides, if you only think of art as an investment, then you have to concede that sometimes you're going to lose your money.