Group of say lets say 6 people come together to set up a ponzi site. They float they cash into scheme, this cash circulates within themselves till an outsider comes into the picture. Once the outsider comes in, their initial position drops from 6 to 5, now the outsiders cash replaces one of the originators capital. now the ratio of originators cash to outsider cash is 80:20; as the scheme gets recognized and the outsider gets more down line the ratio of the originators to outsiders reduces by 60:40;50:50; 40:60; 20:80; 0:100; 0:150; 0:200; 0:250

Their decision to cash out is based on the rate at which the cash is flowing into the scheme, if the rate in which cash flows into the scheme is high, they let it ride higher. And this will happen based on the honest belief of the fools promoting it along with commission promise to only certain. They now decide what percentage of outsiders cash they want to give out and the percentage they want to cash out with.