Do you mean you don't pay 15 dollars and only about 4 dollars? That's weird. May I know what country are you from? Its because when I check the fees. Regardless what country are you from you need to pay 15 dollars and right now its even increases to 30 dollars. anyway here is the okapy withdrawal fees.I dont pay $15 to withdraw funds to my local bank account. Its 35 ZAR so depending on the exchage rate it can be about 4 dollars. If they charging $15 for a withdrawal to the bank that would be a lot and would mean that you need to have a lot of funds and will have to plan carefully when you are going to withdraw.
Withdrawal fees
Wire transfer EUR 1%, min. €10 **
Wire transfer USD 1%, min. $15 **
Wire transfer GBP 1%, min. £7 **
Banking Details Clarification $30
SWIFT Confirmation $30