here's a previous post I made..
Used somebody like them once, about 4 years ago, for a birthday present for my wife. £50ish item ended up more than doubling in price, with the dropbox fees*, shipping, customs and vat and the revenue fee at this end. Took nearly a month from ordering to arrival as well.
*company I bought the item off would only ship to cardholders address, so I had to pay the dropbox company, who then ordered the item for me. This costs, of course.
Might be cheaper now though.
So, if you can pay for the item yourself (ie they'll ship a purchase made on a foreign issued card to a US address) you might be able to get way with avoiding customs, but I wouldn't bank on it. Mine had the valuation (item ocst plus all asociated fees) as the customs valuation. To be honest, if the business didn't do that, they'd be pretty foolish.
It was worth doing though.