Why we should pay 5% to someone to get our money back?
Their bank demand this unreasonable (I can agree to that) fee to transfer the money, and it is written in MtGox's Terms of Service (which you accepted, remember?):
[A]ny transaction fees levied by any bank intervening between the paying bank and the receiving bank (including the paying bank and the receiving bank) shall be deducted from the currencies transferred.
You don't have to. You can withdraw by another method or wait for better times. (Who wants USD anyway? USD will be worthless in just two days.)