I've self-published two books and my economics have been completely different. Since first publishing Mastering Modern Payments in 2013 I've grossed almost $75k

I've self-published two books and my economics have been completely different. Since first publishing Mastering Modern Payments in 2013 I've grossed almost $75k directly from product sales. Of that, I've paid about 3% to Stripe and PayPal for credit card processing, a few thousand for server hosting, and another few thousand for design and editing work over the years.