As a buyer I always offer to cover the fee's if I make a lower offer, 9 times out of 10 it works, have never had anyone offer it in return but then I had someone send me the money for a pistol I sold recently via F&F which took my by surprise I must admit, I put it on a quicker postal service in return so we both benefitted from it.
Fee's do get expensive above £200 so I can understand why sellers try to put it on the buyer but like you say, 10 seconds on Google gives you the fee total and can adjust price accordingly.