Do you think that thre might be something more going on? I don't know what to call this kind of scenario, but suppose that two people are friends and one friend wants to give the other an old car or $200 for some purpose, but for whatever weird unstated reason the friend doesn't want to make it an official donation. Instead, he wants to dress it up as a sale or trade. So he gives his friend the car in return for an overvalued work of art, because artwork can be drastically overvalued due to the subjective value of art.
A simple partial example of the kind of thing where this goes on is with kids selling overpriced stuff to raise money for their school project. The kids' neighbors who buy the stuff don't really want the product necessarily, but they want to help the kid earn money, so they buy it anyway. Sometimes those school sales do have good products though, unlike the taped banana.