There are days with many sales and some painters will pay an agent a bit more. In addition you spend a lot in food and drink here. The heat and the anxiety level both are often high. Before they kicked us out of the Cathedral area it used to be much more. Oh, that is unpredictable.
Tourists are a fairly stingy lot.
There are the factors of quality, size, if painted on cardboard vs cloth, etc. You tend to spend a lot here. It is hard to resist temptation. You have no choice but to buy them. Not all the painters here are independent.