There is always a risk involved in buying used parts. I have given money back for some things that I know for a fact weren't broken when I sold them, and I have also received money for items that the previous owner swore were fine.

Anyone who is honest will try to make right on a sale, because they know that the door swings both ways.

I think it would be fair to see both parties meet in the middle on the cash. This obviously has gotten ugly, and who's respect and dignity is worth $700? Not mine.