I've probably spent about $300 on donations and registrations so far. Blue collar background, so I'm not rolling in it. Then again, it's all very relative. USD = you've got money to spare, generally, even if it's just beer money. I'm not trying to act like I've got some kind of moral highground - I've probably yoinked about $300 in mainstream games and movies off the web - but what can I say? Roguelikes are all about the underdog. I can't bring myself to be part of the problem in those situations.
Plus, I just feel it's very important to support entrepeneurs. The few times I've really tried to build a game, it's been a grueling experience that left me drained and frustrated. People who can keep the vision of a finished project in their imagination while they're slogging through code have my utmost admiration, and the fact that they're doing it all pro bono means that they're all the more deserving of support, since we all get to enjoy the fruits of their labors.