It's obviously a joke, and much more money has been spent on jokes before. It's harmless fun, as he doesn't really claim that the piece of paper is worth
BTC.6. The listing literally says : "You are bidding on a piece of paper with "
BTC .6 BTC" written on it." Things would be different if he claimed that it were a paper wallet to take advantage of naive people who want to get into the game. His drawing in a bottle could be a little misleading though, because the image features a QR code.
Also, the highest bid as of now is a whopping 6 cents, so it's not out of the ordinary. Heck, I would bid if I actually found it funny, or if I knew the person. People have sold stranger stuff before. Lighten up!