(Not sure about the question of multiple story experience in a season. Gut feel, I don't mind.)
I was reading a thread on the Ars Magica forum, and came across this https://forum.atlas-games.com/t/how-much-does-a-teacher-charge/9339/1 description of "root" arts books being cheap. I am presuming that we are simply not using that informal "rule"? (I had never heard of it before, so I am just trying to understand.)