A $20 game... with the complete (awesome) OST for free. No DRM restrictions or special player needed. And you even get a PDF file for printing if you want to make a physical case.
$12 can get you Diablo III's (imo; weaker) OST, and just that. DRM'd with all the joy and restrictions of iTunes.
And Diablo III's OST even has less tracks then Torchlight II's.