My ROI is outstanding. By this time next year, I'll have surpassed 10,000 students taught in my career. And every year, I get a little better at teaching, so my recent classes are even better (potentially at least) than they were when I started.

There's nothing quite like seeing the light go on over a student's head when explaining a difficult concept, so there is also the personal gratification of helping another person better themselves. And this is a positive feedback loop that accelerates my self-improvement over time. The better I get, the more time and skill I have to improve my teaching even more next year.

And the salary ain't bad either.

So, without question, the ROI for both me and my students is excellent.