This isn’t out of the realm of possibility. It depends mostly on the final PPV buys, if it is closer to four million than three million Mayweather will be cashing out. He will be cashing out regardless (at minimum will make over $100 million), but he feels there is a chance he can make $200 million.
In an excellent article by Yahoo Sports, Mayweather and Leonard Ellerbe break down how Mayweather took control of his business and became more than just a boxer.