From the FAQ on their website:
Not regarding to withdrawal method, a fee will be displayed before executing the withdrawal and deducted from amount. SEPA withdrawals are charged with fixed 0.90 fee once your funds are converted to EUR. Minimum amount for SEPA withdrawal is $10.00. International withdrawals are charged with 0.09% fee, minimum fee is $15.00. Minimum amount for international withdrawal is $50.00.
So you've definitely been overcharged.
You can pay and then threat them with legal dispute. They're UK registered and by UK law they need to properly inform you about any fees.
BTW do they provide any receipts with all the fees shown?
No receipts provided. If I want to obtain any information about who took the money, I have to pay 2x30, i.e. 60. But since Bitstamp has no standards for acceptable bank changes, it is useless to pay these 60. I would simply be out $70 more than before, i.e. a total of over $400.
No doubt you're right that one could sue them in theory. But it would not be worth it for $400. What remains is to let others know about their hefty withdrawal fees and strange customer service attitude. [I use the term "strange" because it is hard to understand why Bitstamp would be trying to prevent investigation of theft of customer funds by banks.]
Update: Their manager did offer me a month-long 10% rebate off of trading fees to compensate for this. That was a nice gesture, but kind of meaningless, since I would have to buy/sell almost 6000 bitcoins to recoup the loss.
So what is going on here? Is Bitstamp artificially padding the bank transfer fees to help make up for recent losses due to the hack? Or is it having banking problems, so that it has to tolerate its banks essentially robbing its customers? Or is its management simply too lazy to work out a deal with their bank(s) regarding fees?