As far as i am aware the seller wants you to send money by paypal gift so they avoid paying the fees. I go into paypal and select gift so it does the calculation of how much the fees would be then as PePPeR says if it is more than i feel comfortable loosing i pay the larger amount by paypal purchase of goods.
In my mind i see payment by paypal gift as to mean payment + paypal fees and if that is the case then i am as well to pay by payment for goods and add the fees ontop of the agreed purchase price so i am covered for the purchase.