A deal is a deal. If during the inspection the gun had failed to eject the snap caps then the dealer pays or takes the gun back. In this case the buyer pays.
The dealer, for purposes of goodwill, might choose to repair the gun. But it is his choice. He is under no legal or moral obligation to do so.
I would expect that sometimes a writer of shotgun articles gets the advantage of a dealer's discretion when I wouldn't. No criticism of the practice or the writer. Just saying Larry's personal experience may be different than ours in this situation.