Sounds to me the guy selling it didn't know what he had and got mad because he lost a few bucks?
Many ways to look at this but I don't see the issue.
the guy selling it priced it & got what he priced it at, I don't see where the buyer did anything wrong ...
I'm sorry the seller didn't get the actual value of the item he was selling---BUT--he should have done his homework BEFORE pricing it. I have sold a few items WAY UNDER THE MONEY, in the past, and I don't regret any of those sales as my pricing was reflective of my purchase price. I would assume the same has happened here and there should be no remorse.
The reputation of the buyer should have no reflection on the transaction and should not be called into question unless there was erroneous information given to facilitate the purchase, and this was obviously not the situation.
We all make mistakes in this hobby and at times we have to stand up and admit it. This is one of those times.