It's where the Credit Card is billed to that matters -- I'm pretty sure the $2 is to cover the finance/bank currency-conversion charges (like we are charged when we use ATMs in other countries) and maybe some taxes averaged in.
-- ks
The $2 is to pay for Whispernet, even if you don't use it.
Amazon are paying global roaming charges for Whispernet internationally, which is why they charge $1/Mb for some things outside the US. Since they don't charge for some Whispernet usage, they need to recoup the money by charging extra for books.
If it was for currency conversion and/or taxes, then there'd be no charge for free books.
Of course, that doesn't explain why US customers don't pay extra for buying books outside the US but us foreigners do.
Chris