I'm still mystified...

I generally agree. I will only ask the buyer to pay the paypal fee when I offer payment by check or money order as an option.  for lower cost stuff, I cover the paypal fee. but if a seller is offering a great price then I will still purchase. 

A seller needs to figure paypal fees into the final selling price, which, IMO, should include the fee at no additional charge.  If a buyer wants to negotiate lower, the issue of the fee comes into play.  As Dweller1 pointed out, if you don't like it, don't do it.  

While I find it annoying, ultimately my buying decision is based on final price, not how it is added up to. I’ve noticed more restaurants and gas stations changing less if you pay cash..

It is a pet peeve of mine as well. I am not going to negotiate. I use buy it now button or offer the asking price. If the price is fair I pay it. If the seller asks to pay their fee I skip the ad.