There are a lot of people selling their AMD "Never Settle" GPU game bundle codes on eBay for around $20, which usually include Bioshock Infinite, Crysis 3, Far Cry 3, and/or Tomb Raider, maybe a couple others. That's probably still going to be the cheapest way of getting any of those (particularly Bioshock) for a while yet.
If it's legal, I'd be interested in that.