I'm aware of those big gambling rings, but those figures are likely inflated. Second, someone correct me if I'm wrong, but the figures given are for the gross revenues, not net profit.
A gambling ring with net profits of 2 billion dollars would have to have gross revenues of like 20 billion. Which, for example, would have to have a structure of, say, 2 million people wagering $10,000 each. Color me skeptical.
I'm skeptical also, big difference between revenue and profit and also collecting on all that money. Seems like a big stretch there are so many high stake gamblers.
