I did Dev Bootcamp in NYC in 2015, during what was probably the golden age for these bootcamps. I had a very very good experience, as did about 80% of the people who went through it at that time. The program was hemorrhaging money and was shut down in 2017.
The cost was about 12k for 9 weeks onsite in a big office they rented in downtown Manhattan. Every 3 weeks they had a new cohort, with about 15 students. You could repeat a 3 week section up to 2 times for no extra cost. I got an airbnb in Brooklyn and took the train in. The curriculum was focused on Ruby on Rails, with Javascript in the last 3 weeks.
We had about 5 or so instructors who had real working experience as web developers (so about 1 instructor to every 10 people or so). The instructors were all in their 30s or 40s and were passionate about teaching and had a decent amount of industry experience. They were all sick of doing engineering and enjoyed teaching so were basically taking a break from engineering jobs. We also had a counselor, two administrators, the head of the program, a full time recruiter, and a yoga teacher who came in three times a week.
If you didn't make it through the program for whatever reason, they would refund whatever time you had remaining. If you didn't make it through the first 3 weeks they would refund you 100%. About 1/5 of the people were clearly not cut out for it, about 2/5ths were capable but didn't have much aptitude for coding, and the other 2/5ths learned stuff very fast.
The 4/5ths all managed to get entry level jobs eventually. The people on the low end of that 4/5ths sometimes fizzled out pretty quickly or ended up with support jobs. I know some of them who ended up having pretty good careers as support engineers, making over 100k within a couple of years I am guessing. We all felt sorry for the 1/5th of the people who were just not cut out for it at all. Some of them left but occasionally one would graduate which was a shame because they really had no chance of being successful. There were also people who were not very good but managed to get entry level coding jobs, but I think it was a struggle for them and they eventually left the industry afaik.
Everyone had to really hustle for an entry level job but it was definitely doable. I came out being able to create full stack apps, knew how to build a front end with Angular (very poorly obviously but still) and with a decent enough understanding of how Javascript worked.
The bootcamp had a decent network. It took me about 2 months to get a job making 75k, which I got through a friend at the bootcamp. I managed to get interviews at about 6 or so places leading up to that, but had no idea what I was doing on those interviews. Most of the interviews I think I got from the recruiter at the bootcamp, including one at Bloomberg which would have netted me a pretty big starting salary. About a month into my job my boss remarked to me that I probably would have taken far less than 75k and we laughed about it.
One year later I was making 140k, and today I am making about 70% more than that so yeah, pretty good ROI. I felt like I learned about as much as possible as I could have in this short period. I kept learning stuff afterwards until getting a job, and continued to be interested in learning for years.
I am sure there is still a good business model here. The price I paid seemed like a lot at the time but in retrospect it was absurdly low. I make as much as a doctor now. The race to the bottom some of these businesses are engaging in seems like an awful approach because it is a zero sum game making it into the industry. The rewards are such that if you could get people there with a decent success rate the value of the program would be a lot higher than 12 or even 30k.