Selling fees, and or cc transaction processing fees are a business/sellers expense. They can build these fees into the price of their products so that they make net profit but they should not be passed on to the customer as a separate tax or or line item. Your dealing with a moron seller, all he had to due is list the price of the item a few dollars more to cover fees. He is obviously not accustomed to customary business dealings. Its sounds to me like he didnt even consider fees and was like oops i sold this for less then I wanted too you, but thats his mistake all you owe him is the agreed upon sale price. Personally id just back out of the transaction after he changed the terms, he created a new offer that you can now refuse, the originally agreement is no longer a binding contract