The fee hidden inside a card purchase
When a customer taps a card, the store does not usually receive the full purchase price. The merchant’s payment provider deducts processing costs, including interchange: a fee that flows through the payment system to the cardholder’s bank. The bank that issued the card can use some of that revenue to help pay for rewards such as points or cash back.
The fee is generally calculated as a share of the transaction, though its exact size depends on factors such as the card and how the payment is made. It is only one part of the merchant’s card-processing costs, but it links a shopper’s rewards to a charge paid on the merchant side.
Why the cost can reach cash customers
A store often cannot—or does not—set a different price for every payment method. Instead, it may treat card acceptance as a cost of doing business and build those expenses into the prices charged to everyone. In that case, a customer paying cash can contribute indirectly to the cost of card transactions, even though no card fee appears on the cash receipt.
That does not mean every store passes along the same amount or that rewards are funded solely by interchange. Merchants may absorb some costs, and card programs can have other sources of revenue. But where costs are spread across prices, the rewards benefit goes to cardholders while part of the bill is shared more widely.
Why merchants accept the tradeoff
Refusing cards can deter customers who value convenience or rewards, and card payments can make checkout easier. Merchants therefore weigh processing costs against the possibility of attracting sales. The result is a quiet redistribution: cardholders receive a visible perk, while the cost behind it may be folded into the price paid at the register by cash and card customers alike.
