Actually European prices are around 1:1 conversion. You have to multiply MSRP with exchange ratio and then sales tax. In EU regions where sales tax is high, it costs more, but in some regions it can be about the same.
Then there is an issue or perk that Nvidia availability is often better. You can find plenty of stock and Nvidia puts their GPUs at 'competitive prices'. In this case, they just mirror MSRP in Europe too. For example, 60s series cards always start at 300 euros at the cheapest and then you pay whatever percentage your retailer wants on top of what he gets. Though, that is not the case for their high end which often is slightly more expensive than they should be.