You can already get the mac version on steam through amazon for $15 here.
Yes it says download but it actually gives you a steam redeemable code. Since Bioshock Infinite is a Steam Play title you get both the Windows and Mac versions of the game.
They also have Bioshock, Bioshock 2, and Bioshock Infinite for $19.99.
I apparently posted an affiliate link without realizing it and a bot removed it and sent me a message.... I just copy/pasted the URL from HardOCP where I first heard about it.
http://www.amazon.com/dp/B00DOD0TZG
/dp/
Heh heh
The game is saying DRM:Steam. I think it means you will get a steam key for activation. And if we're understand well, steam will give you all available version of target game (e.g. MAC Edition, Window Edition and Linux Edition) regardless what kind of key you activated that game. To be sure: just send Amazon a question :D.
PS: The Bioshock packed is only 20 bucks too. http://www.amazon.com/gp/product/B00DOD0TZG/ref=amb_link_383705862_2?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=hero-quick-promo&pf_rd_r=1MFT5KA7VFZBJ235QF03&pf_rd_t=201&pf_rd_p=1616675382&pf_rd_i=B009SPZ11Q. Get it and share your Bioshock 1 and 2 keys with your friends.