Kottke points me to this forum by authors talking about getting paid for writing:

I wouldn't be the first writer to point out that doing something so deeply personal does become less jolly when you have to keep on at it, day after cash-generating day. To use a not ridiculous analogy: Sex = nice thing. Sex For Cash = probably less fun, perhaps morally uncomfy and psychologically unwise. Sitting alone in a room for hours while essentially talking in your head about people you made up earlier and then writing it down for no one you know does have many aspects which are not inherently fulfilling.