Any time there's a freebie like that, Gamestop always gets a ton of trade ins. The packages will be open, but you can check the disc before you buy it. And Gamestop has a really good return policy/exchange on used items. Plus right now they're doing buy 2 get 1 free. No reason not to go used.
But yeah, I got my copy on Black Friday. I want to say some stores have it for 40$ and TRU has the buy 1 get 1 50% off right now.