I've came across pump-dump groups on online game markets in the past. While I'm not sure, I think it has the same methods and goals.
You may think you can make big profits, it's kinda unlikely, unless you can outsmart the system. The person who makes the most profit is the one who calls when to buy or sell whatever cryptocurrency, as he makes the first transactions.
Ex. Caller says "buy EOS". The price of EOS will then rise a bit depending on how many members the group has. But before the caller makes that call, he buys EOS first so he gets EOS on lower prices. Same concept when the caller calls the sells.
Yeah, those pump and dump groups make money front-running their own members. That is in addition to the membership fees. I think they are scum.