I doubt they buy all that stuff solely for the purpose of commissions, though. Usually artists with such costly equipment do something art related for a living and need the stuff whether someone from fannish circles will ask them for commissions or not. There's a number of factors you'd all have to consider on both sides of the issue (some artists get their software free from their school, for example or discounts on art supplies), but it comes down to the bottom line that for fanart/fanfic commissions, there isn't a definite difference where one of them is inherently more expensive for the producer. You can't live off of either.

P.S.: I'd say that Scrivener offers a bit more than a "fancy note-taker." YMMV, of course.