The exchange rate, VAT and shipping/ferrying costs will bring the US price up to UK levels with the extra hassle of registering, inspecting and gaining permit approval.
Exactly the (reluctant) conclusion I reached this week. The cost of hunting an aircraft down, inspection and shipping will be the same though whether you buy an aircraft for $20,000 or $200,000 so if you're looking at the the top end of the market at least your costs won't add 50% to the overall price.