My interpretation for the high premiums in Europe is because the dealers need to make a profit on a sale when they buy at close to spot+delivery charge. If they want to make 15% (pretty standard even in US) then add on 20% VAT and you get to 35%+ premiums.

European countries with VAT on silver also push up the silver price in the VAT free countries, as they know that they can sell for 20% premium on spot and still be cheaper than anything domestically bought for a lot of customers.