Outside of medicine, law is the only field where someone from a modest background who went to an average school can work hard and quickly have access to a six figure salary. These ibanking, consulting, private equity etc. positions that you are probably considering a better avenue to high salaries are essentially cut off to those who didn't figure out at 18 that they needed to go to Yale. Top MBA programs and these elite financial companies won't accept someone who hasn't had elite WE; which generally requires that you were hired straight out of undergrad--which means you needed to go to an elite school to be recruited.
This is incorrect. There are plenty of lucrative professions outside if biglaw that are available to state school graduates: engineering, information technology, dentistry, psychiatry, and (as you mentioned) medicine. Consulting and investment banking opportunities are available at (though harder to obtain from) state universities as well. One of my closest friends, who attended UT-Austin, just nabbed a position at Goldman Sachs in NYC. Not bad at all.
If you're a liberal arts major from a state school, yes, law is pretty much one of your only options for the possibility of making a huge sum of money. But, as I've been trying to state repeatedly in this thread, going to law school for just this reason is terrible. I know too many dissatisfied big firm attorneys, both in NYC and in secondary markets, who hate their lives because they went for that reason.
And keep in mind, I said that it's their only option for the possibility
of making a huge sum of money. One shouldn't expect a big firm job. You will suffer through this yourself when you eventually interview, and you end up offer-less because no one can stand your personality. In the boom years, you might have survived, though.