I think that there are some important secondary numbers to crunch here. I am a frequent user of credit cards, though almost never carry a balance. My favorite card has been paying me a rebate of around 2% for a long time. It's actually a large part of the reason I choose to use it instead of cash or checks.
Some of the financials associated with the use of credit cards include fees that the card company receives, interest and late fees, money handling conveniences and efficiencies, probable increased sales due to purchase convenience and impulse facilitation, etc. I can't begin to do the math, but there is more to it than the spot transaction factors. Somehow, my credit card company seems to be satisfied with our arrangement, as am I.
If retailers start to charge me more than the rebate, I will probably significantly reduce my card use, based on a very limited perceptive judgement. I should probably do my own more comprehensive analysis before adjusting my behaviour. You can bet that the credit card companies will do one, and maybe many businesses, as well.
The possibility for unintended consequences appears to be high regarding a gross adjustment in the current credit card swiping fees system.
The 2% comes from the card vigorish. Many Merchants pay 5% in discount -- for a $100 charge they get $95 in cash, while the bank tries to get the $100 out of you. There are other charges but this is the largest one that I know of.
The banks can then use most for income and in some cases send some back to you.
And don't forget the charge-offs the banks have to absorb for bad accounts and fraud. That comes out of those fees.
The merchant is getting squeezed. And that ends up with the customer taking a share of the pain.
When you look at it from the perspective of the merchant, there is something entirely different going on:
The merchant knows most people want to use plastic. Plastic costs, so he sets his prices to cover those costs. That means that the person paying with cash is helping to cover the costs of his credit transactions. So the merchant can now differentiate: he can pass all the credit costs onto his credit customer and the cash customer gets a break.
There's an example locally. Two gas stations, on opposite corners. They both charge exactly the same for gas. One takes plastic, the other takes cash. Which one do I go to now? The one who takes plastic, because, like you, I get 2% back. Which one will I honor with my business when the one starts charging 5% extra? I don't know, but I know I will be paying cash or using my debit card, from which I receive no cash back.