Chesebert, I definitely acknowledge the role luck plays in my success (and in everything), but to be clear, this is not an "outlier" situation. I wasn't trying to say that you can go to any regional law school and expect to land at a top firm--there's a very important point missing from that: this method only works if you go to a regional school that is LOCATED IN a second or third-tier city where some top firms HAVE OFFICES.
Here's an example to show what I mean. We can both agree, no doubt, that Jones Day is a top law firm, right? They're huge and they pay well over $100k to students right out of law school (I think it's in the $130k-$160k range, depending on "market," i.e. depending what city the office is in). If you want to waltz straight from law school into a job at Jones Day in New York, San Francisco, etc., then yeah, you need to go to a major name-brand national law school, because everyone wants to live in those cities and competition is fierce.
But Jones Day has an office in Cleveland. And if you look at their website--if you go to the "people" section and run a search on "Case Western," which is the local regional law school--you'll see that this world-class law firm's Cleveland office has tons of lawyers who graduated from Case Western. Why? Because unlike New York, Cleveland is not a city that anyone really dreams of living in, and the last thing a law firm wants to do is hire a new grad from Harvard or wherever, spend hundreds of thousands of bucks in salary and benefits to get them trained as a competent young lawyer (which takes a good 2-3 years or so), and then have them up sticks and bolt for another firm in a fancier city. They prefer to hire people with demonstrable local ties, because that greatly increases the chances that those people will stick around long enough for the firm to start getting some payback on what it spent training them. And so big firms with offices in these second or third-tier cities will do on-campus interviews at the local law schools, solely to hire to the local office.
And once you're hired locally, if you've been there a few years and are doing well I've seen cases where the person wanted to move to a fancier city and the big firm, rather than see them go, gave them a job at the firm's office in said fancy city. So you can end up debt free and working right next to the high flyers with $200k in loans, or you can stay where you are and have a great life earning a ton of money in a secondary and much CHEAPER city.
So that's the path I followed, but it's possible to do something like that with major national schools too. For instance, my sibling went to a major national school and got a big-firm job in a fancy city right out of school--but the major national school gave him/her a free ride, because he/she also got into Harvard and the other school, seeing that he/she was obviously Harvard material, offered a free ride if he/she would come to them instead. That's how it works: if you can get into a school that's ranked X, you can get a scholarship at a school that's ranked distinctly lower, and if that lower-ranked school is either (1) still a name-brand school or (2) in a secondary city where the firms you want to work for have offices, you're good to go.
As for whether it's Mustachian (since you said "going for free is not mustachian if you can otherwise make $50k/year"), there are a couple reasons I disagree with you there.
First, there are still many six-figure jobs out there awaiting freshly graduated young lawyers; in secondary cities those jobs tend to pay in the $110k-$130k range to start.
Second, before law school I could've made $50k working in advertising (I interviewed for such jobs, and indeed years before law school I held one for about three months until they started layoffs), but there's a definite ceiling on what you can earn from such jobs; there is no point where you can make partner and suddenly vault into the mid-six figures or low sevens, and your options if you do get laid off or want to work independently are more limited. I mean, the worst-case scenario other than prolonged unemployment is you end up temping, but lawyer temps earn way more than graphic design or copywriting temps.
Finally, corporate jobs usually treat employees in a very undignified way--in particular, layoffs happen with no warning or severance pay (big law firms usually give lawyers a few months' notice). That can be financially and emotionally very difficult, and it also makes it harder to get a new gig (whereas if you're a lawyer knowing you're likely to be canned in a couple of months, you apply for new jobs from a position of power: "currently employed").
So it may look like an apples-to-apples comparison NOW, but the $50k law job and the $50k corporate job are not really comparable long-term.