I agree that money in does equal money out. If we all put in $100 combined then that would surely be a $100 paid put to us. If we were the only people in it and no one else joined then this is the way it would stay .

If other recruits join during that time and put in another hundred then that would be 200 out split amongst us. If the circle starts to shrink during this time the top 1% would be forced out (us), leaving the rest to find new recruits.
While the circle is growing however, everyone is making money. It is only when that starts shrinking that money will start being lost. The bot would be attached to the blockchain as a permanent fixture so it would surely go through phases of growing and shrinking.

This would leave it up to the people within the system to ensure its growth and maintain their profits. If a group of people did not work to make it grow by even 1 recruit per week or any set number, then they would flatline or maybe even loose a small investment.

The bot could possibly sit dormant for months or even years after a flatline while users are making nothing or breaking even. One recruit could come in and recruit many others which would then bring up a spike due to their hard work. No, of course everyone won't win in the end. But not everyone will lose either. When you are amongst hard workers it could be a winning situation