Someone wrote, "I think one thing that needs to be emphasized is that MMM assumes that readers are in a relatively high income household, preferably one with dual incomes and no or few children. The basic core of the message is "make a lot of money, but live as if you don't, and invest the surplus". Sometimes people show up with three kids and a household income of $30k and expect advice that will enable them to retire in five years. The math doesn't work."
I strongly disagree, and I don't think people making $30k or less are typically that delusional. When I started reading MMM I made minimum wage, and I knew immediately that there was no way I'd be able to retire in 5 years. Many of the articles on cutting back (and many forum threads) didn't even apply to me: I already wasn't eating out, I already didn't have a car, I already didn't go on vacations. I was already working 7 days a week and picking up doubles. My problem wasn't keeping up with the joneses, it was buying food without relying on credit cards.
I stayed out of debt by living like a rat, but I tracked nothing and had no plan. Because of MMM I switched jobs, my husband went back to school (community college then state school, graduated with $6k debt which we paid off before interest kicked in), I learned that investing isn't scary, I learned to think about spending differently. I went from feeling depressed about not having what others had to realizing I was kind of a badass! I'm all about stoicism!
Now we're making more money and on track to retire by our early 40s, yeah that's way later than MMM and his lady, but for a couple that started at minimum wage it's pretty fucking awesome.
(sorry for weird formatting, when i tried to do a quote it was all wonky looking)