I think he is just using this for fluff/backstory more than anything. But I could be wrong.
Trainers have a Training Source Quality of 8 to 10. Teachers have a Teaching Source Quality of 6 to 12, plus the bonus for single-student teaching. Magi charge a very high price for teaching another magus for a season (the equivalent of 4 to 10 pawns of vis). And they might combine that teaching with the season when they teach their own apprentice.
Yeah, though that appears more toward teaching for gaining experience. Which is great but not exactly what I'm looking for.
I'm not sure what a breakdown of spell levels learned would look like for that price range. One could assume that the low end of instruction at 4 pawns of vis would have something of an "average" mage vs the high end at 10 pawns for a season would be more of an optimal specialist in the subject matter you are looking for (high arts + applicable focus + lab bonuses etc.) though translating that into firm numbers is tricky. I'm a little hesitant to weigh in too strongly on this topic since I'm the one looking to try and use it.