I had a similar experience with something I bought at Montgomery Ward several years ago. They gave me double the refund coming to me on an item I took back. It was a clerical error and I didn't realize it until I got home and actually counted it up. Of course all these thoughts pop up in your head about keeping it, using it to pay bills, buy something you need, etc., but like you Squeak I just shoved those thoughts out of my head and straight away went back and showed them what occured and like your situation they were utterly amazed (jaw dropping astonished) that I would bring the money back. They thanked me profusely for returning the $200 odd dollars to them and in doing so I would never have nor linger to have a guilty conscience if I'd kept it. The right thing to do is ALWAYS right!

Best regards,
Mike