Bioshock 1 and 2 are $5 each on Steam
I don’t think Andrew Ryan would approve of such dirty capitalism, but what is he going to do, build his idea of an underwater utopia? In case you don’t already have them, the PC versions of the first two Bioshock games are currently on sale on Steam for £3.49/$5 each. If you have three other friends who don’t have Bioshock 2 then you can also get a four pack for £11.24/$15.
Bear in mind that are various reported problems with the PC versions of both games so do your research before plunging in, especially given that the console versions are pretty cheap anyway. I haven’t personally played the second game but I can definitely recommend the first game if you’re looking for a truly unique game from this generation. No I didn’t play System Shock 2.