It’s entirely dependent on the market and region. Sometimes it is cheaper to go to the dealer depending on make and model. It also depends on where you live and the availability of mechanics and parts.

Sometimes they’re even worth using for “normal” repairs because they will sometimes bill by the book even if the actual labor time is higher.

This is exactly correct. Which is why if you aren’t sure, compare prices with your preferred mechanic first. Where I am, the best independent mechanics and shops charge more than the dealer, for various reasons.

My experience is that independents are significantly cheaper on a like-for-like basis, are also more willing to do a workable partial or alternate repair, but have worse lounges and often no courtesy car. (So you’re getting something for the extra cost.)

The closer the person who does the work is to being the person who writes the bill the closer you get to clock time in my experience.

https://www.liveabout.com/the-truth-about-flat-rate-car-repa...

Many mechanics aren’t really directly employees of the shop, and often get paid based on work they get (some even have to “rent” the stall). It can be an interesting industry.