Here in the UK (and I think the same applies for much of Europe) we have the annoying situation that ebooks are subject to the full rate of VAT (17.5%, likely to rise under the new government to 20%), but physical books are zero-rated. This is related to an EU directive that HarryT refers to elsewhere - EBooks are regarded as a download, like software.
Geo restrictions notwithstanding, I try to get as many books as I can in the US as not only is the price cheaper most of the time, the tax is lower too.
