Why do people think that GS does YMMV?
GS rarely ever does sales that vary at specific stores. There are only two instances where they do.
-B2G1 or some overall % off for certain items (usually always used games) when a new store opens up in that area, but this is not price related, but promotion
-Opened items that get like a minor 10% discount. Those are of course YMMV because each store carries different stuff that is opened.
Go to gamestop.com, check the price of a game, and then you know if it's a mistake or not. Simple.