I think we are pretty close to agreement here. I'd be interested in what you have experienced in the realm of front-end testing though - whether you think things are just as cut and dried in that realm (that's another discussion though).
And I'll also accept the point about skill in test writing that improves the cost-benefit analysis. I'll also cop to not having that kind of practiced ability at testing to the level I would personally like. But it's chicken / egg. A lot of folks get their start at scrappy start ups that can't attract the best talent. And just can't afford to let their devs invest in their skills in this way. Hell - even established companies just grind their devs without letting them learn the shit they need to learn.
I feel a victim of this to some degree - and am combating it with time off work which I can afford at the moment. One of the things I'm working on is just understanding testing better - y'know, so I can in the future write a SKILL.md file that tells Claude what sort of tests it should write. lol...
https://news.ycombinator.com/item?id=3033446 - Linking to this old comment because it links to each of Ron's articles, a discussion about it, and Norvig's version.