XCOM: Enemy Unknown is poised to go on sale this Monday on Amazon for 66 percent off. That's 17 bucks, I think. Killer deal, no? I could be wrong, but I think that's the lowest it has been.
This is all hinging on this silly vote over on Amazon's facebook page: http://www.facebook.com/AmazonVideoGames?v=app_153839431317646&rest=1
You have until Sunday to vote. So far, XCOM is beating Civ V by A LOT. Not surprising.