A friend of mine wanted to take some pictures of him holding trained pigeons this one Ukrainian had. I paid up, and then asked him to break the 50 euro bill I had into two 20s and a 10. He then gave me the 20 back... only to ask me for it back because "that's his price."
I would've decked him or sprinted away, but I was going to get paid back by the friend anyways, and I didn't want to end up in a French jail cell.