Some thoughts:
1. Dev Bootcamp in specific seems to be geared to beginners. Which is great for a beginner but not so great for someone with even some experience.
2. I've sat in on some of these programs, and even in programs that bill themselves as faster-paced the majority of students will be beginners. Which means that to a certain extent many things will have to be geared towards the lowest common denominator and a lot of time will be spent going over things that you already grasp well, while comparatively less time will be spent going over more complex topics.
3. The programs do help with introductions and they do a lot of heavy legwork in reaching out to employers. However, at the same time, the process of getting a job is, as I imagine (I have no personal experience with getting a job through this process), very much like a career fair type affair. I doubt the introductions will be the kind of quality/personal introductions that provide an advantage in applying. The introductions alone are nearly certainly not worth $12k+.
4. I think that as long as you have a marketable core skill (iOS, Android, Rails, Django, frontend JS, backend JS, etc), you should be able to attain the same job connections by attending engineering meetups and events in SF.