FYI, watchbuy prices include all taxes, except if you live in north carolina. I have 2 friends who ordered from them (NY and SFO), and they were not charged a dollar more than the actual price. It would be different for Canada though.
Now, just for fun, let's take the Weltzeit:
WatchBuy: $5700
NOMOS Store: 4080 euros, which is $5440.
If you consider that taxes are roughly 18.7% in UE for luxury goods and roughly 17% in North America, this gets to 0 (basically, if you could order from UE, you would pay it without the UE taxes, as for Stowas, but then would pay the US tax when receiving the package, 'pretty much' getting to the same price). Now, let's not forget duties, pretty much 5% additional on watches, which means $272, surprise, 5440+272 = $5712.
Are you sure the prices are that crazy?