This happened to me too. I was going to use my paypal account to pay, with no credit card. He still told me it was 50c to do that. This is from ebay regarding that policy. Sounds like it's okay as long as he charged for cash or credit card.

A surcharge fee cannot be added to the price of goods or services that you purchase on your MasterCard card. Here are questions to help determine if the fee being charged is a surcharge.

Is the fee added regardless of whether you pay by cash or credit card? If so, it is not considered a surcharge.