The UK price including sales tax, while the US are not.
A 64GB PB cost about $330 incluing tax in US and 16GB about $220 in most States.
Yes, but US customers can benefit from non-sales-tax online vendors. Of course, you are responsible for the use tax, but most people don't pay those anyway.
But our European friends should not feel disadvantaged as they generally pay less in terms of income/payroll taxes relative to the States.