It was the same in Indiana. Most commonly gas stations charged two prices, one for regular and one for a cash discount. The reasoning was that they weren't making enough profit from fuel to cover the cost of the credit transactions with the price of gas as it was. The cards had different tiers for the fees, and when gas went up, more common people went over into the 2nd or 3rd tier.

Additionally, some small restaurants and shops did the same thing. Usually these folks get charged more for processing credit cards than the large places.