This is how the video game-only stores operate. How often do the clerks try to hard sell you on game guides, used prices, preorders, game guards, etc.? That's where they get their largest profits. They make very little on the new items, but the markup on used is incredible.
So while technically you saved some change, they can point to how many game guards they've sold. They didn't profit on the two they sold you, but they're now on the quota.