Costco's business relationship is with a processing company named Elavon. The rates they advertise in large print look attractive, but few, if any, of the transactions, will qualify for that rate. This is a "tiered" pricing agreement where a low rate of say 1.5% - 2.5% is used to induce new customers to sign up. The processor uses its discretion to decide which transactions will qualify for that rate and which will be assigned to the qualified and non-qualified tiers up in the 4% - 5% range. Most transactions will be mid or non-qualified, especially where the patient, client, or customer us using some type of rewards credit card. This is the bait and switch technique that all processors using tiered plans employ.