A store that sells a lot of big ticket items pays only about 1%. But you could always ask for that discount anyway. Having worked in a gun-store, I know the manager was always happy to come down a little on any gun that expensive.
In any case, even cash has costs (as **IAmNotSpartacus **noted):
hold-up insurance increases significantly when you have a lot of cash on hand.
banks will charge a small fee for depositing cash for some retail customers.
(depending on your account and how they charge you. Of course, certain retail customers don’t pay that fee, they just pay a larger monthly fee, but in the end, the bank does charge a bit for large cash deposits, maybe $5 per $10000)
there is a greater chance of being robbed, and you lose more.
if you have a lot of cash, you hire an armored car service- they ain’t cheap.
extra time after closing to count, recount and confirm cash totals= more wages.
and employee defalcation rises and gets more expensive when it does happen.
Thus, in the case where the average sale is pretty large, it can be more expensive to accept cash than CC.
CC fees are a *very *small part of overhead. The big items in overhead are rent and salaries. Asking “How much do credit cards add to the cost of general merchandise?” is like asking how much does free coffee and donuts add to the cost.
CC fees can be compared to advertising. Sure advertising adds to the cost, but usually it pulls in far more business than it costs.
Now, that being said, I do have sympathy for the dude who has a lot of sales under $10. He’s taking it in the shorts. While we know that “no CC on sales under $10” policies aren’t right, I would go along cheerfully with a sign that said "CC fees are very expensive on small sales. So, if possible, we’d prefer cash to CC on sales under $10- but if you only have your CC, we’ll gladly accept your business either way. Thanks!"