To start off, skill classes offer a base pay that is multiplied according to your tutoring sim's skill level, ranging from x1.2 at level 6 to x3 at level 10. While this system functions well for most skills, it presents an issue with vampire lore: once a sim reaches level 11, their pay drops back to the amount they received at level 5 (from §360 to §120).
p.s. I know game isn't out yet but that's what I found in the source code