Yes, the buyer always pays shipping. Even the very popular Free Shipping really means the cost of shipping has been included in the asking price.
Free Shipping gives the seller a discount on the fees she pays when she uses it.
I think what you are talking about is the duty and tax charged on payment under the Global Shipping Program.
This was institued in part to encourage US sellers to sell internationally, a way of increasing eBay's business by making international shipping painless.
It has been badly explained to US sellers, who are currently the only group who can use it. (There are rumours it may be expanded to EU sellers.)
The Global Shipping Program does not require the seller to ship by Priority Post*. The seller ships with Delivery Confirmation, widely available for USPS services, to Pitney Bowes who trans-ship from Kentucky around the world.
The extra money charged is for duty (if applicable), sales tax and a $5 (ish) fee to PB.
Makes no sense on items less than $20
EBay does not encourage using the GSP on items valued below $50. They don't do it very well , however.
I f your seller is demanding that you pay for Global Priority (not GSP) you can ask (before bidding) that she ship by First Class International. Let her know that this service carries up to four pounds of product and is Delivery Confirmed to Canada. It is also much cheaper than Global Priority.
She is not required to agree. But you already know what to do about that.
