If you live outside of the United States, and purchase an item from a U.S. seller on eBay, and they will only ship via USPS Priority Mail, they have a very good reason for it.
Personally, I print all my postage labels with Paypal, and Paypal only allows for international mail to be sent using Priority Mail, therefore I must charge $10.00 to ship an item outside of the United States.
Some people will write and ask “why can’t I just pay you $3.00 and you send it by regular mail?” — well, because that would actually cause me MORE work, and I don’t want to do it. My auctions are a business, and my business has routines, and it is just a hassle to break that routine.
If you buy something from a US eBay seller, and they don’t say how much they charge for international shipping, CONTACT THEM and ask before you bid or purchase the item.