Here is what I am going to do if I ever get charged eBay fees for an off-ebay sale.....
The eBay user agreement requires disputes be settled by arbitration. ebay.com link: policies
As part of the arbitration agreement, eBay agrees to pay the arbitration fees, which from my understanding are about $1,000. Yes, you read that right....$1,000. If eBay charges you fees for an off-ebay transaction, dispute it in writing, as required by the User Agreement. Tell eBay that you want to take the matter to arbitration. According to the User Agreement, "If the value of the relief sought is $10,000 or less, at your request, eBay will pay all filing, administration, and arbitrator fees associated with the arbitration." Once they see this, eBay will immediately return the final value fees that you were assessed. This has worked flawlessly with numerous other companies that require arbitration in their terms and conditions.
You can thank me later.