In the case of NBA 2K, it doesn't give you any DLC, what it gives you is not only the four days early thing, but also gives you stuff worth like a months worth of grinding to level up your MyPlayer or start your MyTeam at a way higher level than anyone else. Since most of the people in this "market" play those online, it's basically like if there was twice the cost Call of Duty that started you with half of everything in MP already unlocked.
They used to let anyone who preordered start early and also gave you gifts to advance yourself with the more expensive editions being heavier on the cosmetic unlocks especially shoes, but they cut it way down this year and only allowed you to preload four days early. A few years ago the preorder bonus let you jump like 17 levels in MyPlayer, this year it let you go up like 2.
