Paris museum pass

I read on a blog that a traveler had bought his Paris museum pass with cash (54 euros)and had been told by the ticket person that it was a good think because if he had used a credit card it would have been over 60 euros (forget the exact amount). So to verify this: If you buy the paris museum pass (4 days = 54 euros), is the 54 euros price still the same whether using euros or the credit card
OR does the point of sale increase the price (as a service fee and to cover credit card expenses for them)? Not referring to MY credit card's fees because it does not have fees. I'm asking about the point of sale. Just verifying the credit card price.