I don't think it should be so clear cut like that. The credit card processing fees charged by the processor is a cost of doing business and should just be factored into the pricing without being explicitly passed on to a subset of customers. For example, a shopping centre or convenience store may have toilets that only a subset of customers would use. Should the customers who bought something without using the toilet be "subsidising the cleaning costs"? If a store offers online ordering, should customers who ordered online be "subsidising the rent of the physical store"?
It's a valid business decision to NOT charge extra for the toilets, too. Just like shops usually don't charge people who are a bit slower in the checkout line more for taking up cashier time.