Green Man Gaming has Bioshock Infinite for the PC on sale for $13.59 right now (66% off). If you use the voucher code GMG20-7EKXF-UTQXX you can save another 20% off bringing the price down to $10.88.
This is a Steamworks title and requires a free Steam account in order to play. This offer is available for 24 hours only.
This is for the PC digital download version of the game only. Prices in GMG are in US dollars and exclude tax.