Are you sure you are not referring to the 2.5% paypal fee, that used to be taken from your payment at time of sale.   Ebay fees then accumulated and you were billed separately by ebay each month.

Now no paypal, and ebay takes there full fee at time of sale.

In any event, the scale of fees is fully known prior to listing.  After all you agreed to the T&C's when signing on to managed payments, and you agreed to the listing terms again when you listed the item.

No point crying after the fact.