Shloulet: I just looked, and the cheapest one is 89 cents, and ships for four dollars. However, I once saw it for one cent, and $1.50 shipping. It does go down pretty far.

Steam and Ebay are the only two sites I ever see mentioned, and Amazon really deserves some recognition. It might not be a direct download, but if you can wait two weeks, you'll at least get a sound track, plus there's nothing harassing you to get more stuff from steam. No steam-style "recognition" or whatever it is either, I guess it's really down to what you're into.