The numbers were not meant to be significant. What I meant was that people would have some combination of a flat fee (like they do now) and a fraction of future income (which they don't now). It would be a good signaling device -- a teacher confident in his ability to educate students well might accept less cash for more future income -- which would signal to parents and students that the teacher was, e.g. likely to add 5% to the average student's future income, at which point the Equity Equation applies (http://www.paulgraham.com/equity.html).