On second thought: the green button has two possibilities. 50% of $50 million and 50% of $0
The expected value:
1/2 x $50 million + 1/2 x $0 = $25 million
This means that if four people hit the green button ($25 million x 4 = $100 million), two of them will win $50 million. Another two will lose. If six hits the button, three will win, another three will lose. And so on.
