A third party amazon seller has the PC version of Bioshock for $1.88 with $3.99 shipping for a total of $5.87 shipped. Pretty good deal, IMO. Link below.
http://www.amazon.com/BioShock-pc/dp/B000MK694E/ref=sr_1_5?ie=UTF8&qid=1309914870&sr=8-5
http://www.amazon.com/BioShock-pc/dp/B000MK694E/ref=sr_1_5?ie=UTF8&qid=1309914870&sr=8-5