Without getting into too much detail, this is a road I’ve been down too, tho not with either meth or AA. I think the biggest thing is, sobriety is usually about rearranging your entire life. For most addicts, a huge part, usually a majority, of your life and mental space is ensuring you’ll get your next drink/hit/whatever. Then when you try and quit you suddenly have this void where all the time you spent feeding your addiction, you just have nothing. It’s why so many programs like AA and rehab spend so much time giving alternative structures, until you can stand on your own and organize your own life. That’s why the guy saying that $11 each week kept him going rang really true to me.
As for cost, like every study ever conducted shows the costs of diversion is vastly less than the material and social costs of incarceration. Think about it, for an entire year of peeing clean, the state gives this person $600-ish. Googling tells me that’s about the cost of 2 days incarceration in CA.
edit: there’s some other points I didn’t really address. You can’t really stop someone from falling off the wagon and going on a very dangerous bender, short of actual incarceration (your old tolerance is lower now but you have the same habits so you can easily OD; sadly it’s not uncommon). But that’s not really the most helpful way to think about it. For the people who are trying to use this program to get clean, being treated like an adult and having the ability to structure payments how it works best for you is a good thing. It’s baby steps into self-management and planning.