You clearly have much more of a direct personal experience / knowledge of Banksy's history than I do, but I feel as though he's using the spotlight in order to make a point about how money-hungry the modern art world has become. Yes, you could take the cynical side and assume he really is just doing these 'exposure-stunts' as a way to make more money, but I'd like to believe he still stands for his anti-establishment message.

As an aside, I thought much of his art (especially vandalism) doesn't actually belong to him, and he doesn't see the proceeds.