I'm slightly confused as to why the Macbook is a lot cheaper in the UK to the US - we're both going through the Credit Crunch and it appears I could fly out to the US, buy a Macbook, and then fly back and still have money to spare compared to if I buy it in the UK. Here's the comparison at today's exchange rate:
From the consumer side, instead of removing 17.5% VAT, simply ADD state sales tax if you're considering taking a pleasure trip and purchasing while here (you may have to hide it in your hat returning through UK customs;-). State sales tax vary: http://en.wikipedia.org/wiki/Salestaxes_in_the_UnitedStates .
Easy really: put the macbook and it's accessories in your luggage and if you're randomly selected for inspection they'll think it's your computer (no VAT). If you enjoy retaining the packaging then break the box down so that it's as small as possibly and post it. An empty box will not be too expensive via sea. 🙂