Didn't Team Fortress 2 did the same thing with the Magnanimous Monarch hat which was also $100 and supported the Relief Effort during the Japan Earth Quake?
It's like those Armstrong Bracelets or those pieces of papers hanging in the Super Market when you donate.
I got the other two hats and the other two Noise Makers though, I donated $30.
Even though your not directly helping, and you won't see your dollars actually doing something, knowing that it did something good in the end is something that I'm for.
Though $100 or even $75 for a single in game item, that doesn't really give you anything, except something to enjoy your self with, seems like a retarded purchase.