He's milking you through shipping. It sounds like he's not happy with the sale price as he felt it was worth more. There is no way that the shipping can cost that much. If he did not state a shipping cost on his site, I think you could demand a receipt of the actual shipping cost. He's probably going to try and add a handling fee to all of that too. Contact Gun Broker and see what they suggest. They are pretty good about straightening out something like this.