I make $40k after tax, in Russia, employed locally, and while that doesn't sound like much to an American ear, I've bought my apartment for $90k a year before. I seriously doubt anyone is going to pay me $400k before tax in the US as you suggested. I'm 32 by the way. And I never work more than 40 hr/week.
I don't see how you can underpay a dev in Russia. Maybe you can by hiring in really small and depressive towns? Or promising rocket science job?
That makes you a rather expensive employee if the company hiring you actually pays your pension contributions, EI, medical bills, and other quasi-tax charges (which are much higher than in the West.)
24k a year is what a good grad can expect in a company that pays taxes in full. The full cost of employing such a guy will be right about $40k
It's frequent nowdays to be cited your salary before 13% tax.
Yet, but the prime majority of all that wonderful digital cornucopia is being developed by underfed and underpaid devs with level of technical comprehension comparable to people called "jquery monkeys" in the West. By the time most of them reach late twenties, more experienced ones will move on to become professional devs abroad, another will, sadly, join the socioeconomic construct/caste of "going to nowhere 30 somethings." You guys in the West complain about age discrimination and skill obsolescence only by the time you hit forties, fifties, if not sixties, but here people hit the same stage much earlier. Companies do not pay for skill even 1/10th of what an American Dotcom would.
What makes a seeming difference in the level of quality is that experienced tech people are found more evenly distributed than in US where Dotcoms and well funded companies vacuum significant portion of any much senior developers on the job market, or in China where Alibaba and Tencent literally employ double digit of all tech workforce and almost all real talent. Here, the fact that a software developer is just yet another "nothing special" white collar occupation somehow, counterintuitively brings some benefit.