> If coding is easy, how come programmers were in high demand, and have demanded large salaries for years (even before ZIRP)?

My take on that question is that programmers were in high demand because, for the last 60 or so years, it has been cheaper to write software for general purpose computers to automate things that were done by people and more rudimentary machines, e.g. accounting, manufacturing, music production, etc than it was to pay the people to continue doing those jobs. So, it continues a trend for programmers to be replaced by software, at least until something in the process breaks.

At its core, there is something difficult about programming. Fred Brooks talked about the need for perfection, Don Knuth about there being about 1 in 50 persons who had the mindset for computer science. But we haven't really been paid because it's difficult, we've been paid because we're cheaper than the alternative.