two suggestions:
(1) someone suggested adding this to the eBay auction description:
"We don't take Paypal and pass the savings on to you."

(2) I'm unsure of this, but I think it is illegal (or whatever) to charge extra for those who use credit cards, but someone suggested giving a discount to eBay auction buyers who use checks or money orders (instead of PayPal). Thus, a seller could have a separate Business PayPal account for eBay auctions and not get hurt with the fees.
"§ 1666f. Inducements to cardholders by sellers of cash discounts for payments by cash, check or similar means; finance charge for sales transactions involving cash discounts"
http://straylight.law.cornell.edu/uscode/html/uscode15/usc_sec_15_00001666---f000-.html

Robert