Loss leaders aren't as common as you would think and isn't specifically a "loss" but more like less. They will sell an item and a fraction of what they could but still make a profit on it. The problem with the cards is that most people don't understand that when you use your card the processing company takes 1.5-3% of the sale, and that is off the total including sales tax not just the pre-tax price. So the company is losing money just to let you have the convenience of using your debit/credit card. That is why you see a lot of places that don't accept American Express because they take 2.9% period and you will either pay that or not accept their card.