Indeed, I get what you're saying, and maybe it's just a way of looking at things, but if you don't at least roughly figure the average cost of your mistakes into the price that you charge, eventually you'll go out of business. A mistake on any single order might still be a loss, but you make it up with a hopefully larger number of successful sales.

For instance, the widget that I make, I screw up a small number of them during production, and I consider that to be part of my cost-of-goods. The rare customer with a complaint gets a full refund. My overall profit more than covers the occasional mistake.

Some other things that the big retailers do is simply not to sell goods that are open to dispute. Home Depot would look at making a pizza by hand from scratch at a retail location and delivering it to your door, as some kind of crazy.