>That doesn't mean the course creators aren't still doing well.

There's almost certainly a power law effect. I'm sure a (small) subset of people who do training/consulting/writing/instruction who have managed to build mostly fairly small-scale but very respectable businesses. The nice thing about video training course is that they're probably a better way for a solo practitioner to scale than most other things out there. Assuming they have the skillsets/talent for it of course.