For example, one key part for me was that the school allowed me to practically don't go to classes as long as I could prove that my work wasn't affected. It's something that you won't find everyday. I'm 100% sure I'd have failed university otherwise because the lack of freedom would have bored me to death Conversely, friends of mine have dropped from Epitech in the first two years because they didn't get enough support, so it shows that the most interesting thing the school has to offer is its learning devices. They understood that one size doesn't fit all (which is against the French public school philosophy).
So yeah, the tuition is expensive (and frankly given how the school works you sometimes wonder whether they eat luxury cars for lunch), but there's simply no public alternative.
One other factor I've also wondered is if people paying for their scholarships weren't more invested in making it a success? I knew my fair share of people who weren't thriving as developers at Epitech as well, mind you, but most of them dropped before the end.