Being a musician is a scalable profession, similar to being a book author (search for Nassim Taleb's definition of scalability). Most scrape by at the bottom all their life, but once in a while, someone breaks out and their income eclipses everyone else's put together. For example, JK Rowling's Harry Potter series.
It would be interesting to see this data broken down by genre. For example, rockers vs. jazz vs. classical. I have no real idea who of those three makes the most / least and whether there is much variation among the genres.
