What makes you think that most artists are rich? Perhaps they are rich in the sense that most of them live in the developed world and so they are richer than those who live in developing countries, but other than that, I doubt most of them are rich in the way the word is typically used. Middle class is far more likely with some being poor and a minority being truly rich. Heck, most artists tend to be young too and they tend to have day jobs which more often than not don't pay much so it's quite likely that many of them don't have any significant wealth or savings.