10^9
Found this remarkable little quip on Quora:
“To accumulate dollars at the 10^9 level all you have to do is come up with a 10^10 idea that will make your investors and perhaps a few key others wealthy at the 10^8 level, make a few score of your early talent wealthy at the 10^7 level, make hundreds wealthy at the 10^6 level, pay a lot of people at the 10^5 level, pay a lot more people at the 10^4 level all with a product that will offer millions a 10^2 advantage or tens of millions a 10^1 advantage. Then, get at the end of the line, keep your fingers crossed and wait your turn.”