[gwbas1c]

It's because the areas around the US that employ software developers are expensive to live. Software developer salaries are similar to what doctors and many other middle class people make.

What pushes salaries into the higher part of middle class is demand and value: It's very hard to find good, trustworthy software engineers who can work without lots of supervision, and the overall value of the work to the company.

I tend to point out that software is an "economic force multiplier." The value of what software implements (automates) is often many multiples of what the engineer is paid; so why would a software engineer accept a low pay to work on low value work?