I think I paid something like $70 for overnight shipping to TN w/$1k insurance on the last gun I shipped. It can be expensive. You can check it yourself. Go to the UPS or Fedex website and run a quote for overnight with the approximate weight and size of the box and it'll tell you what the cost is.
If it comes out much lower - call the seller on it
If it comes out about right, you know where he's coming from and you can probably work with him to find a cheaper shipping arrangement.
The thing is he is refusing to work with me, so I'm assuming he's trying to screw me based on not getting what he wanted for the revolver. If he was on the up and up he wouldn't be refusing to give me an itemized list of what is costing so much and he would put me in contact with his FFL so I can inquire about cheaper shipping.
Here is his shipping terms:
Buyer pays actual shipping costs for the following option(s): Overnight, 2 Day, 3 Day, Priority Mail
No international shipments.
See Item Description.
Sounds like you have a choice that his is backing out of.
Complain to GB, neg rep the jackass, and walk away.