Earning $500,000 per year isn't that hard
Good programmers are actually really undercompensated. A decent 5+ year experience programmer, given appropriate work, is worth $500,000 per year. Maybe 2-3 times that, even. I'm not talking about celebrity engineers, either. I'm talking about solid people who probably spent a fair amount of time learning off the clock (or, on the clock, because the best way to learn the value of an education is to steal it from a boss) but aren't "brand name" programmers. The best programmers are worth $3+ million per year. Software victories are huge for the business.
Decent financial quants get $500,000 per year, including bonus. You have to be strong, but you don't need to be a "rock star". I know smart people you've never heard of who are earning $300k-1.5M as quants. Unlike in the Valley, where you need to be a 10x self-seller and put up with VCs and become a celebrity to make any money in code, you can get moderately rich just by being a good programmer in finance. (Some people say that programmers are second-class citizens in finance, compared to traders banking millions, and that's true; but they're third-class citizens compared to founders and VCs in the Valley.) As a pure programmer, you need to find a niche that finance demands (e.g. C++, low-latency programming, and perhaps Haskell in a few years). Or you can study the mathematics and become a quant. This shouldn't be taken lightly; if you're working full-time, it'll take 3-4 years of self-study, or 2-3 with an MFE or similar degree, to get to the point of basic mathematical readiness. My advice, for those considering that path, is never to lose the mathematical sharpness.
The quant path, by age 40 or so, will get you near or past $500,000 per year on average. All that said, it's an open question how long quants will continue to be well-paid. I think their outlook is good, because they're actually worth that much, but market conditions are hard to predict, 10 years out. In 2008-9, it seemed like the high compensation of finance people was about to end, and that it would become "boring" again. Conventional wisdom was that quant compensation was going to crash. It didn't. In 2014, good quants still command high salaries.
By the $500,000 level, you have to be able to take leadership roles. This doesn't mean that you must be a full-time manager, but you're going to be MD-level and you have to be seen as someone who could run a team if needed.
Outside of finance, $500k usually requires getting into management, unless you become a celebrity programmer, and as others have pointed out, that usually comes from options or RSUs. I have no idea how to make "celebrity programmer" happen. Being good at your job is only a part of it. Or, you can go into consulting and you'll make $500k (and possibly more) in your best years, but it won't be reliable.
As for how to get to $3 million? No idea what it takes to get there, because it's incredibly rare for a non-managing programmer. I suppose the best route would be to start your own consulting business, kick ass, and start taking on more people as the workload swells. Again, you're transitioning from an individual contributor to a manager. The good news is that, if you're willing to grow a little slower, you can hire only great people and then your management load won't be that bad. You might be able to continue writing code and learning (from people you hire, who'll hopefully be better than you at a few things). That means you won't be able to hire just anyone, so it will mean growing at a slower rate than you see in an r-selective VC-funded company. (That said, VC's pretty much a non-option for a consulting firm anyway.)
Quick summary
The highest paid coders work for investment banks (and other entities in that sector). developing high-frequency trading algorithms. The best algorithms bring in billions of dollars, and the people that develop those algorithms are well compensated. There are a set of high performance server programmers in the financial services industry, based in NYC, that work on multi-million dollar, multi-year contracts. They have been hired for the specific talent of provably providing the highest performance code for algorithmic high performance trading. They tend to be Russian.
$500k is just $250/hour for a normal 2000 hours of work a year. Not high for unique expertise. Get every Cisco certification and five years security experience and that would be your rate for charity projects. Or write a great framework that efficiently solves a common problem and easily hit that rate on consultations.