Why is it that convenience stores have signs that read "Debit card minimum purchase $15" or "Credit card minimum purchase $5"? And, if there is a good reason to require a minimum purchase amount, then why the difference between debit and credit methods?I guess Im confused. Does Visa/MC charge more when one pays with their PIN (debit) versus without (credit)? Dont merchant banking fees include a flat transaction fee plus a percentage of the purchase amount? What does requiring a minimum purchase help to defray on smaller transaction amounts? It seems to me that requiring a minimum transaction amount only pads the proprietors pocket. Does anyone know whats the real/actual motivating factor(s) in stores requiring a minimum purchase for credit cards/debit cards?.--Answer1:Being able to accept credit/debit cards is definitely not free for merchants. Ive never noticed a difference between credit and debit amounts..--Answer2:You already know the answer. That transaction fee can be 75 cents or a buck. So the shopkeeper does not want people using a debit card for a newspaper or a pack of gum where they only make a few cents before fees. On a $15 purchase they make a few bucks, so that they can pay the fees and still come out ahead by a little bit.