Easy A - https://easy-a.net/

The website provides a semester simulator that can (accurately) predict student grades, workload, etc for a given course / semester.

It also provides a breakdown of the grade distributions, work load (in hours), difficulty, etc. For every course, professor, and combination there, for universities on the site.

Profitable is relative, I spent around 100 hours tossing the website together and make maybe $100+ a month with a freemium model. I have roughly 2500 active users (not all paying), with zero put into advertising. There is probably potential to grow this, but thus far prying money from students is painful.