International shipping is expensive. Try figuring out a typical package weight for a standard order and go to USPS.com and "calculate a price." Pick a few random places- Australia, the UK, wherever- and find a zip code for them and see how much it would cost.
Then, I use that as a ballpark so that my shipping is set up as 1 price for US, 1 price for Canada, 1 price for everywhere else.