AuctionCut

I sold a pair of weber carburetors on ebay the other day that were listed at fixed price rather than an auction format, the buyer paid immediately through pay pal and a few minutes later I contacted the consigner who I was selling the carburetors for to inform him of the sale and when I gave him the part number of the item I sold he said that they should not have been sold but that the carburetors that should have been sold had only one digit difference in the part number and when I inventoried his parts I mistakenly chose the pair of carbs that were NOT intended to be included in the to be sold list. This took place in about a hour and half after the item sold , so I immediately reversed the pay pal payment in full. Having done this I was just about to call the buyer when he called me, I explained what happened and that I was sorry for the inconvienence but with the part number being only one digit different from the pair that was to be sold it was an honest mistake and the consigner does not want to sell the pair that was listed. I was curious as to why he didn't want to sell them and found out that they are extremely valuable and worth 10 times more than the pair he intended to sell. I contacted ebay to inform them what happened and they advised me to email the buyer a form to ask his permission to cancel the transaction , the from was received back saying he would NOT agree along with a note from ebay instructing me to follow through with the sale. I then sent an email to the buyer stating that again I was very sorry for his inconveience but his money was promptly refunded and the matter was out of my hands and the consigner of the carbs did not want to sell them.. Two days later, today I received an email from the buyer saying that he hired an attorney to represent him and that if I didn't want to go this route I was to call him, i immedately emailed him saying that again I was sorry for the circumstanses that took place and urged him to look for another set of carburetors and that if he thought it warranted hiring an attorney that that was his choice and I would certainly not stand in his way but there was nothing at this point that I could do to remedy what took place and that the consigner did not want to sell the carburetors that I mistakenly listed and that he could clearly surmise that it was in fact an honest error, that while inventorying the items in the consigners garage I included an incorrect pair of carbs that again were oNLY ONE digit different than the intended pair, what more can I do at this point its honestly not my decision. So as of now thats the last communication from the buyer saying that he hired an attornet, obviously my question is am I liable for this error and what can he do to me? any insight would be greatly appreciated.