I can say this, as a pawn shop owner for 20 yrs, I don't believe there is a business going that doesn't carry two sets of books, because of the tax situation, not only the mob, but millions of small business owners deal in cash, if small business went exactly by the repressive tax code, 90% would be out of business tomorrow,

as far as how much they make, probably only they know.
now, the old mob, Costello, lansky, profaci. luchesse, Gambino, and the rest made 100s of millions, and their families may still be trying to hide it.

the mob now is in a much more dire situation, the IRS operates outside the law, and they have no oversight.