Couldn't work out a trade

I recently saw a coin that an on-line dealer had listed. It looked fairly nice and so I contacted the dealer with a few questions. He answered them ok, but I had an additional question as I wanted to trade a piece that I had picked up an upgrade for a while back. He would not give me a firm trade value until he could see the coin, which is understandable. When pressed for a ballpark pending a final review when he had the piece in hand, he came back with a very low amount. I was hoping for a split the difference kind of deal since he would be making money on both ends of the deal. Interesting as his prices usually are on the high side. Oh well, guess I'll have to try again. Maybe trying to trade is not the best way to dispose of an extra coin. Maybe my expectations were too high.

Does anyone have advise on how to go about working a fair deal out?