Paypal charge for the use of there service, simple.
Gift payments are fine if you know the seller or there feedback is excellent etc etc as no comeback if it goes missing bla bla(send recorded of course).
Pay the fees if your unsure etc, there is comeback/protection of sorts.
I have done many sales and normally i include the paypal fees if its only a cheap(few quid) item.
On a car its more like a 5'r, so depending who is buying/selling, its really up to them if they accept the fees as a discount/loss or insist on them being paid buy the buyer.
Old school sales, like send a chq, wait 5 days for it to clear after being paid in and then send the goods are really just out dated now.
paypal immediate and a bit like accepting a debit payment without being ashop etc, So its ideal for transactions. The fees are not much really, so I advice always pay paypal normal unless you know the seller. Simple.
Paypal payments are just easier than anything else now. Accept we get charged. and either pay them or dont. Its the modern way.