The problem is that many buyers of fairly expensive items don't carry a lot of cash, or must pay on the "installment plan" (i.e., by credit card). Others prefer to buy by credit card as a "safety" factor in case they need to enforce some sort of warrantee issue, or for return purposes. The retailer pays for the convenience to both himself and the customer with a percentage of the sale.
Not sure what the retailer can do about this, but if there are no other reasons for the cancellation, they ought to see what their legal options are. Getting this on Fox may also have some effect, especially if customers and other retailers "vote with their feet" against the credit card company. Wish the shop luck!