You couldn't, I couldn't, but he can.
You couldn't, I couldn't, but he can.
I don't think I'd get away with that, so why should he?
I guess the big question is does what he has done to the images count as derivative works or not? I say not, since he's used the image unmodified.
I hope at $90k a sale it catches the attention of a pro bono for a nice test case. Would be interesting to see what the courts say.
Everything else is more or less secondary, both to the market and to the artist as product and manufacturer. In other words, a lost/settled/won lawsuit is not a liability for him.
I think that he's got a pretty good chance that he'd win based on the history, and lower damages in the case of a loss. (Not registered, not otherwise commercial work, no potential loss of sales for original)