For its newsletter subscribers only, Newegg offers downloads of Bioshock: Infinite for Windows and Mac for $9.99. Coupon code "EMCPGPF98" cuts it to $7.99. That's the lowest price we could find by $17. Coupon expires March 10.
Note: Although the product pages state that these games are for Mac, the codes will work for Windows too. These games require a Steam account for activation.