Amazon currently has Bioshock 2 for $13.99 (prime eligible) for the PS3 and 360.
On the PS3 page, it shows that this is a Gold Box deal and that the discount is available for a limited time. IMO its worth $13.99.
:360: Bioshock 2
:ps3: Bioshock 2
Edit: the PC version is also a great deal...