Hmm, according to the article in the new yorker the food costs for doing it oneself is 50 dollars a month and it was a significant time saving from making food or going out to eat, now if I figure out that it actually works as advertised - why wouldn't I just do what the original inventor did instead of buying it?
Prep time? I like to cook a large pot of chili or a stew for the work week. It's still a tedious thing to procure the ingredients and make it, even if all the prep is one afternoon and 2 minutes of reheating each work day. If there's no single source for the ingredients you need to establish a purchasing routine and a time every week or month to mix up a new batch. Compare to just ordering it if the markup isn't too high.
