There are several reasons why Teslas are more expensive in Europe than in the United States, namely the transport cost, import taxes, local VAT and exchange rates.
At the moment of writing, all Teslas are produced in the United States (more factories will open soon around the world). This means that all cars need to be shipped to Europe. This additional cost is added to the price.
The European Union (and the countries within) charge tariffs and import taxes to protect their own economy – making Teslas a little bit more expensive than in the United States.
Value added taxes (VAT) vary across European countries. For example: in Hungary there’s a 27% VAT, in Luxembourg only 17%. This makes Teslas more expensive in certain EU member states.
Finally there’s the exchange rate. Prices are converted from U.S. dollar to euro, pound sterling or another currency. Exhange rates will vary over time.