Best Buy -- and all retailers -- occasionally sell something rather cheaply to get people in the door.
This sale was probably decided upon before the game even released. (I have seen Best Buy offer a game on sale on release day, only to reset the price the following week.).
Thus, sales this early in a game's cycle, especially ones that are announced in pre-printed circulars/newspaper advertisements, cannot be used as signs of poor or lower-than-expected sales. But they are certainly worth taking advantage of if you can.
Mike from Morgantown