I took the first interesting offer that I got, when I graduated from college. It was $43k. (You have to start somewhere!)
But, as you get more experienced you must also learn to understand the value that you provide to the companies that you work for. Too many developers get taken advantage of. Software currently rules the world; remember that. Companies make trillions of dollars (in real revenue or efficiency) on the things you create. You deserve a good pay, if your products are valuable.
I'd also like to underscore the comment in your parent post--"good enough for me." It's not always about pay. I'm seeking a sort of "medium chill"  existence. I currently make more money that I ever thought I would, but I also have a position with a relatively stable company where I can continue to do interesting work without unnecessarily ramping up my responsibilities with each pay increase. If you offered me a job with a 25-50% pay increase with a similar increase in work time and/or stress, I'd politely decline.
A college professor that I had (a mentor), once told me that the best programmers should be somewhat lazy. I'm definitely not a 'best programmer', but I do try to automate as much as possible and be on the look out for 'gordian knots' to cut.
But, I rarely find many, if any, gov't contractors at the HN meetups in DC.
There are actually a lot of startups here, and lots of VC money, in general. A lot of people come here to live, and work from home, here. Housing prices and costs of living are high, but not as high as some other locations (SF, NY, etc.).
So, definitely other factors, too.