On the US site, the price displayed in 399USD. For countries that use the euro, it's selling for 399EUR. That's 447.16USD. If I was looking for a new phone and considered this one, I'd be annoyed at the price difference.
US prices are exclusive of sales tax where applicable, in the EU you have on average about 20% of VAT (which is always included in the MSRP) on consumer electronics, the EU also has on average higher import tariffs than the US.
The price i see in the UK is 309GBP which is 435USD which is actually less than 399$ + 20% VAT, so oddly enough the Yanks are the ones getting screwed in this process if you believe that VAT is justified.
For the UK at least the price is about identical to someone from NYC buying the phone for 399$ + ~9% surtax which is about 435$.
Aside from taxes, which others have mentioned (and I believe the standard in Europe is for prices to be tax inclusive), the EU typically has stronger consumer protection laws. More refunds/replacements/support etc. means higher cost.
On the US site, the price displayed in 399USD. For countries that use the euro, it's selling for 399EUR. That's 447.16USD. If I was looking for a new phone and considered this one, I'd be annoyed at the price difference.