Why is the "hardness" of the work the key criteria? If you compare "value to society based on peoples willingness to pay", then the ratio of that between a billionaire and the median person probably is 8000x - the founders that become billionaires usually capture only a tiny fraction of the value they create, but we tend to take that value for granted and it's hard to measure. So we only see the billions of dollars they have, not the 10s or 100's of billions of dollars of value they create.