Wonga just got into trouble in the UK with this advert, but... Using a bank overdraft can be as expensive as a payday loan. According to "Which" Consumer Magazine in the UK, borrowing £100 for 31 days will cost £30 with a Halifax authorised overdraft or £20 with some Santander accounts. Borrowing the same amount for a month with Wonga would cost between £20 and £37.