Why do some companies charge different prices for cash and credit purchases?

Cash is an acceptable form of compensation to pay all debts, public or private, "legal tender". Credit is only an equivalent. Merchants charge higher prices for credit in order to defray some of the costs associated with accepting credit cards. A merchant (grocery store, shoe store, etc.) decides independently if they will accept credit cards as a form of payment for goods and services rendered. Once a merchant makes this decision, he/she must then pay a series of other businesses (equipment lease to swipe the credit cards, payment processor to coordinate the actual account debits and credits, etc.) a small amount for every transaction paid by credit card. Many merchants do not charge more to accept credit, as they consider it just another cost of business. Many merchants also do not charge more for credit card purchases because it is prohibited in their Merchant Agreement , and they could lose the entire ability to accept credit cards if they are caught doing it. Visa, however, does allow its merchants to offer a "cash discount" off the marked price, but not a credit premium, so the customer is never charged more than the marked price.