This sounds less like “publishing a book” in the traditional sense and more like “becoming an education and training entrepreneur.” (Which is fine if you enjoy that kind of thing, but seems like the book part is only a tiny % of the work involved.)
When you use a publisher, you only have to write the book, and the publisher will take care of editing, printing, distribution, marketing, advertising, etc.
When you self-publish a book, you need to do way more than just writing the book. You have to do all the things the publisher would have done for you.
By self-publishing, you can get 80 or 90% royalties, instead of 10%, which I think it's worth. It might not be worth for everybody, but, considering how much time I put into writing the book, I wouldn't be happy getting just 10% profit.
I wonder how feasible it would be to write a (great) book, skip most of the coursework/training/audience-building bits, market it using more conventional means (reach out to journalists, etc.), and make ~$10k?
Personally, as someone who loves technical writing but less the people bits around it, I'd much prefer doing something like this to "building my brand" and essentially becoming an instructor. (This is roughly what I ended up doing when releasing my first iOS app, though the journalist cold-calling was arduous and questionably reproducible. The success I had was mostly on account of Apple taking notice, perhaps with a small push from positive blog coverage.)
Right. This is why you partner with someone like me - because we already have an audience, a process, and some capital+labor we can use to help produce & promote your book/course.