I believe when he said it was violation of store policy it was that the guy only gave him 13 dollars?
$13 was the return rate on a purchased item. He was asking specifically to sell it, not return it. That difference means, even if they know the game is completely unused, the fact that the higher-ups and such can't confirm it's still in top quality means it goes for the reduced priced. Even so, he's selling it, so it'd have to be below the full price.