To be most accurate, those aren't the payment processing fees either. They are the blended rate, which include interchange, the payment processor's cut, the assessment fee, etc.

Most people don't know what a blended rate even means, though, so why bother using that terminology when I'm trying to save some smallco engineers on HN a few points on their startup's margin?

Feel free to replace my use of interchange with 'blended rate' if that helps.