"Merchants hand over some $138bn in fees each year; according to the National Retail Federation, a lobby group, it is their second-biggest cost after wages."
Unless they're talking about more than just credit card fees? From the same article:
"But credit-card fees are unregulated and meatier, usually sitting at about 2% of the transaction and rising to 3.5% for some premium-reward cards."
Are they saying that retailers pay less than 4% of the retail price to acquire their goods? They pay more for credit cards than rent?