Yes, of course customers are ultimately covering all costs of doing business, this included.

But not specific customers. Affluent consumers often use credit in advantageous ways. That behavior is subsidized by consumers of more limited means. I get 5% cashback every time I shop at amazon, 6% at every grocery store, 5% on every tank of gas and 2.5% on every restaurant, etc. (Sallie Mae Rewards Card, Amex Blue Preferred, Sallie Mae again, and Chase Sapphire, respectively). Access to credit most certainly costs me "negative money."