At a previous employer, I did some work, over a three year period. (Custom reporting system, nationwide, 10,000 people fortune 500. The system was used by hundreds of managers and above, and professional workers (think 7 years of college or more). Shortly before we were laid off (the IT dept was outsourced to Cognizant), there was a bid for re-writing the system. Cognizant came back with a quote for $20,000,000. Yes, that's 20 million dollars. That was in late 2008. As of last year, a director there told me they are still using my system, 4 years after I left, and zero maintenance had been required.
I made 65,000 per year for four years. What do you think I should have made, money-wise?
At my current gig, same thing. Billions of dollars at stake, and I single-handedly design, build, deploy (one-click -- the power of scripting) and maintain systems used by over 1000 people, from executives to line workers. What is my true worth to the org? Do you think they would pay be $900,000 a year? Even at that rate, they would still make money off my work.