The very fact that this question has been asked demonstrates the reason that the biggest companies are founded by people who are truly "not in it for the money."
Most of the numbers here are under $10 million. Bill Gates, Steve Jobs, Michael Dell, Mark Zuckerberg, could have all sold their companies very early and had plenty of F-U money with a few extra Lamborghinis to boot. But it was the vision of creating something bigger than money that kept them going at it, even though it could all fall apart, and that's why we have the amazing things we do today.
Thanks for your comments, and I appreciate your point, but I think that it is a little too simplistic. There have been many great entrepreneurs who sold a company and then used their newfound position to go on to create even better and more important companies.
Tony Hsieh created Link Exchange in the 90s, then he sold it to Microsoft, and then turned around and created Zappos (which he recently sold to Amazon).
The paypal guys sold to eBay, and took their money to start all sorts of new ventures (off the top of my head, I can think of Elon Musk (Tesla, SpaceX), Max Levchin (Slide), Reid Hoffman (LinkedIn)
Is your suggestion that they should not have sold PayPal? Were they just "in it for the money?"
An entrepreneur who sells and has enough money not to worry, can continue to start businesses ad infinitum which puts them in a potentially better position to create "something bigger than money." If Elon Musk had stayed at PayPal, I doubt he would have started a satellite launching company as well as Tesla Motors!
Most of the numbers here are under $10 million. Bill Gates, Steve Jobs, Michael Dell, Mark Zuckerberg, could have all sold their companies very early and had plenty of F-U money with a few extra Lamborghinis to boot. But it was the vision of creating something bigger than money that kept them going at it, even though it could all fall apart, and that's why we have the amazing things we do today.