The credit card companies will *Fuck* You Up if you're not careful.

http://money.cnn.com/2013/01/27/pf/checkout-fee/

Now credit card fees can be passed along by merchants to customers. Watch your merchant. Watch your bills. Maybe ask before you buy.

We made a purchase today at a local small business. I asked the guy if he was passing along the fees. He said he would not. He feared pissing off his customers by appearing to nickel and dime them. Besides, the fees were already covered in his pricing structure.

I dare say pretty much NO one will lower prices by 4% and then pass along fees on credit card purchases only. So anyone charging the fees is likely to be fucking you.