I've taught as an adjunct or equivalent at three universities. Two public, one private. Two gigs were during the school year, and one was an abbreviated summer program.

I don't remember the summer program rate, but I recall the school-year rates were around $3,500 per course. That was fine if you had a full-time day job, as I did, and the classes were in the late afternoon or evening and your employer didn't mind your moonlighting.

I taught the classes because I enjoyed the experience, not for the money. I've met plenty of people in the same position: Peter Thiel presumably did not teach his now-famous Stanford course for the salary. So to that extent, the Trinity administrator quoted in the linked article is correct.

But I suspect most adjuncts do not have non-academic careers. So they're struggling, especially in expensive metro areas (in part because they're competing against people like me that might be convinced to teach a single seminar for virtually nothing if we get to pick the topic). But it's a bigger problem than that: as <bloataway> suggests, it's middle management bloat, coupled with an oversupply of qualified instructors, government-subsidized loans, etc. Not a simple problem.