Ask HN: How much would you pay for a serious online course?

Fellow hackers, I am a former academic and current data scientist. I have been getting feedback that I explain technical and mathematical topics well for a few years but never took the comments seriously.

I am finally considering putting together courses on topics in machine learning and optimization that are hopefully both detailed and practical but start from first principles. An example is a course on discrete optimzation using simulated annealing. Ideally, I would like to put up the content on Udemy (infrastructure/marketing taken care of but they take a cut) or host my own site (I keep the profits but have to manager everything).

Towards that end, how much would you be willing to spend for a course ($0 is a perfectly acceptable answer)? I see people put up courses for $100-$200 on Udemy and that seems really high to me but maybe people do pay that much.

The end goals are 1) to demystify some of the topics that I enjoy, 2) to supplement my full-time income so I can scale back full-time work to do more open-source work and teaching.

Thanks in advance!