One of the great things about online coursework is that it requires less staff and everyone can work at a different pace. From what I've read/heard 42 Code School has very little staff and mostly relies on computer courses and peer learning.
Why would anyone pay for online course work when there is so much available for free from places like MIT and Stanford? I paid for a boot camp to have access to an instructor with industry experience. Not to learn language syntax and build projects.
I think the main advantage there is the peer to peer learning and long hours. There's group projects. Yes, your coursework is all on the computer, but you are there morning to night surrounded by people doing the same thing, so you help each other out. That also ends up being a great network later on, which is one of the best things people normally get from college. They also have some special industry guests. Even Paul Graham was praising it. https://twitter.com/paulg/status/847844863727087616?lang=en
You have to pay for travel to get there and food, though they do have a fairly cheap cafeteria on site. Also if you need a visa they can't help you with that, they are not an accredited school.
Check out the FAQ for more questions https://www.42.us.org/admissions/faq/
42 is free to attend though so if you're talking how they fare as a business, it's funded by a billionaire.