Why do merchants not give discounts for cash purchases?

A few traders will in fact give a cash discount, but don't expect it to be great as the credit-card companies only charge the trader about 3% commission anyway. Any significant cash discount is more likely to mean that the trader has no intention of putting the sale "through the books", but in that case don't expect a receipt! Another point to bear in mind is that if the trader is one of the many high-street stores advertising "interest-free credit" it is actually illegal to give a discount for cash or any other type of immediate payment, as to do so would imply that the full price DOES indeed include an element of interest, and so cannot be properly described as "interest-free". Retailers price the item as a single, cash sale basis. That is the expectation and anything else takes the adjustment. They make additional money on credit sales when they are the ones extending the credit. (Essentially, credit is another product). The incentive of making more sales (that is product and credit), may infact motivate a lower combined price. (Many companies, expecially consumer retailers, make more on the credit they charge on their own cards/accounts than they do on the product they sell). Sales on credit cards issued by others (Visa, Mastercard) are generally at the cash price, (although the retailer pays a fee to the credit card company who takes the risk and costs and effort of providing the credit, essentially to facilitate this sale). Finally, in non retail, more trade situations, discounts for cash, (actually fast payment, normally check), say within 10 days of the billing are very, very common. Many of these bills are sent on a "2% discount if paid in 10 days, total due in 30 days" called 2/10 N30 billing. Very common. That a company takes the discount offered is a sign of good financial management and ability.