Actually Gloria, the way I understand it, the buyer doesn't pay anything. You are automatically put into the plan, and if you want out you have to PHONE them to opt out.
It seems a wee bit tricky in that if a buyer says your item isn't exactly as you stated, you are automatically having to prove yourself, and the decision is made by Paypal, not you the seller. Much more complex than I just stated, of course, but if you check the .com PS board, you'll see a lot of info on it.