Jo: He means that you charge additional fees when customers purchase premiums by credit cards. For example, the 30 days premium membership costs 14.99 USD (with service charge 2 USD), but the premium page shows 12.99 USD only. He wants to point out it's a failed price model and it's harmful to sales. In addtional, it seems that he misunderstood what the service charge is. He mentioned it's because of the currency exchange but I don't think so.
BTW, the BitPay payment method doesn't work.