i agree with the consensus that you shouldn't pay a previously-undisclosed cost. more fundamentally, i've always found it tacky for a seller to lay off paypal fees on a buyer, much as i would object to a merchant laying off credit card fees--paypal is largely a convenience to the seller by enabling immediate, verified payment and various other protections.
Seller asked for PayPal fees after the sale. Should I pay them or not?
I recently purchased an item and after accepting my offer the seller asked for PayPal fees (3%). I checked the listing and nothing was listed in the ad about my paying the fees. I have already payed half the fee but I'm not sure if I should have paid the full amount. Changing the deal after accepting the offer feels wrong to me. Looking for guidance.