Well even if you included digital PC sales the sales don't come close to the PS3 version of BF3.
Why? There's many reasons.
-Consoles have a much higher userbase
-Piracy on PC is extremely easy
-You need a powerful PC to run BF3
-MMOs are the dominant genre on PC and with the recent popularity of F2P games, its going to be really hard to get people to buy stuff.