This sucks, although I agree with the Global shipping program being shit. I get similar complaints about shipping from Canada being more than they expect from the US sellers.
Via USPS I rarely get charged customs (<5% of the time), and when I do, it's never anywhere close to what ebay charges. Minimum shipping for a blazer to Canada via the GSP is $26, way more if it goes above $100. It's impossible to compete in bids with US customers when I have to pay 25%+ shipping rates.