Assuming you are talking about new US built boats, you are about right - a $100k boat in the states will probably be £90k-£100k over here.
Dont forget, boats in the states are advertised ex-TAX as each state has different sales and luxury taxes. Also, US manufacturers have added cost of transatlantic shipping and import tax over here.
If you look at the EU net cost compared to your US net cost you are looking at $100k being sold here for £69k plus tax and shipping
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