International shipping from US is insane. I can ship at 12x6x2 package that weights 1.5lbs from one end of the USA to the other, and will costs about $9, tracked, insured and 2 Day delivery through USPS. If I want to send the exact same item to the UK it is going to cost me $23.00, no tracking, no insurance and it will take 2 weeks to be delivered (again, with USPS). If I want tracking, double that price. The cost of international shipping is insane. I don't think it is the same going the other way, though I'm sure it isn't cheap either.
EDIT: I should note the prices I quoted above are when I go direct to the post office. If you buy shipping labels on line and print them yourself it is slightly cheaper but for international you still have to do all the customs forms as well. Which, you as the seller are responsible for.