That sounds like a violation of the Visa/Mastercard agreement. Those networks do, in fact, charge the merchant for the use of the network but their licensing agreement specifically prohibits mentioning that surcharge or passing it on to the customer. Instead the allowable method is to provide a "cash discount."

That surcharge is also why most credit card terminals default to debit card when presented Visa/MC debit card is used. Debit cards incur a lower fee from the network than the credit card fee. Of course the customer also has less recourse using debit vs credit when it comes to chargebacks, extended warranties, etc.