Taxes On Stuff From The US

If you can find an item at the right price in Europe it already includes all taxes, there's no customs clearance fee and the shipping cost is significantly less than from the US.

My last few courier shipments from Teleskop-Service all cost 18 Euro, the last shipment I got from the US by courier cost $60 - which is $72.60 when you add VAT. So let's say that item was listed at a value of $500 on the website, the total cost would be:
Price - $500
Shipping - $60
Duty - $21
Subtotal - $581
21% VAT - $122.01
Total - $703.01
In Euro - €540.78 (assuming $1.3 = €1)
Then add €18.15 for the clearance fee incl. VAT, the full cost of this example becomes €559.03.

Let's suppose you could get the same item from a Eurozone shop and the shipping cost would be €18. If the list price including VAT is €541.03 or less you are better off to buy in the Eurozone. On top of which if the Eurozone shop provides a good after-sales service and the courier service is reliable you might be willing to spend €10-20 extra.

The $500 item in this example might not be such a bargain

There is value to be had from Eurozone outlets but don't expect goods that are ordered from or distributed from the Sterling area to be priced competitively in comparison to direct imports. For some reason, despite the fact that the UK VAT rate is just 17% the prices are not as good for non-EU products as outlets in some Eurozone countries.

One honourable exception I've found to the UK pricing problem is in the legitimate market for SLR cameras and lenses, if you compare the pirces at shops like Grays of Westminster or ffordes of Beauly for current DSLRs and lenses to Eurozone outlets it's difficult if not impossible to find a better price, though they may be beaten when products are end of line.