When I purchase something from somebody here using PayPal, PayPal asks me if it's a "personal/gift" payment or if it's a payment for merchandise. If it's merchandise, they charge the fee (which someone else already posted). They don't charge fees for personal transfers of money.
For personal transfers of money, there's no need for a shipping label so PayPal doesn't show that option. For merchandise, the seller has the option of printing out a shipping label.
Everything is dependent on how the buyer answers the question when making payment. If the buyer does not specify "merchandise", then there is no PayPal buyer guarantee on the purchase. Some people here are just nice and want the buyer not to have to pay the fee; however, they may not realize they then have no protection if something goes wrong with the sale.