Given the performance of Google's auto-captioning, I suspect developing worthwhile auto-captioning is pretty difficult; according to [1] the better Youtube channels use gig economy captioning at $1 per minute.

Of course, there would be some scope for efficiency - no need to pay for captioning when the performers aren't speaking!

[1] https://www.wired.com/story/problem-with-youtubes-terrible-c...