If I wire you $650, either I pay the initial wire fee to my bank or else that fee is deducted from the $650. Then the bank converts the USD to EUR. The rates won't be nearly as good as you see at a forex broker. Walk into your bank, ask how many Euros you would get for $650 and how many dollars you would get for 500 Euros and you'll see the difference.
Then there can be fees charged by the intermediate banks.
Ask your bank to pull up as much data as they can on this and see if they can find out more about how 50 Euros got nibbled away.