i bought a chain device from us ebay once cos it was waaaayyyy (about 45%) cheaper including postage than the same one even from crc/woolyhatshop.
Then a card turned up, inviting me to 'cough up and pick it up' -import tax payable on the postage as well as the product (I can understand the tax dodge you could have done by undercharging for the product and overcharging for the postage) plus customs/RM handling fee made it cost me about 40 pence more than if i had bought it over here. And with all that my 45% saving disappeared and it took 2 weeks longer to get to me. You live and learn!
( I have often wondered if this very calculation is used to set the price for fancy US made stuff in the uk, ie make it cost around the same as it does bought direct from the usa with all the postage/tax/handling on top and then provide a local warranty service. Whether that bears any relation to the 'trade' cost of the product to the importer could be completely incidental!)