Printers are basically sold at a loss.

A more apt analogy would be selling you a laundry washer/dryer for $100 but only accepting name brand detergent pods.

Or, what Keurig tried to do to coffee, though even they sell the machines above the printers margins.

Printers get away with it because unlike your car, laundry, or coffee maker, most people don't actually use the printer very often and can't be bothered to raise a public outcry over it.