I agree that money is not the sole motivator. It was not for my dad. However, he might have left if his salary had been cut in half.
I have a friend who worked at Bell Labs for a long time and who has a number of patents in his name; however, as a condition of employment the company keeps any money earned from the practical application of the patents.
The perks of the job - ie creating cutting edge technology - was more important than $$$ to him.