In your mind of mind, don't you realize the only person knowing the size of your paycheck is the only one who could determine who could afford to pay what? That is in addition to technical issues, such as actually holding the loans for say, 30 years, and not beholden to investors for a quick flip profits. And that person is who? That's what I thought.
I was a grasshopper who asked if the cost of originating and portfolioing that loan was $108, how come the borrowers only pay us something worth $101-102? The answer is never that complicated, as one learned later in life.