The reward is the power to do what you want, and bend the world to your whim. Money is the enabler of that. And yes, I think that the power to do what you want is a very large driver for people like Jobs, Musk, and Bezos. If you prevent them from getting lots of money for their efforts, you necessarily limit their ability to gather power. Everyone seems to always think that money is for getting a faster car or a bigger house, because that's most people would buy a car or house if they had money, but that's not really the primary driver past a point.

I had a teacher in highschool that put it this way (paraphrasing): "After a certain level of wealth, it just becomes a game and money is just points to keep score."