bro there are many different types of BF3's out there.
1: Standard edition,costs arnd 1.5k new if u buy urself and little more if u get someone else to buy it for you. It has nothing extra,just the SP campaign and the norma few maps for MP.
2: then there is Standard edition PLUS back to karkand i.e B2K. With this,u simply get the B2K maps and few new guns and vehicles which can only be used in B2K maps. Many people confuse this with Limited edition but it isnt.
3:this is the real limited edition,costs arnd 3.5K i think. Includes standard edition,B2K maps and Physical Warfare pack which includes dogtags,some guns and a few other things i think but i dont remember correctly.