The 'small-scale' 100k-1MM per participant per day per casino laundering can add up to 'real money' quite fast.

The larger-scale money laundering in my area is a but more complicated, involving import/export schemes, real estate transactions, and property developments. I'm not in a mega-city, so I assume these schemes are taking place at a larger scale in those. I have only ever heard of very basic and stupid schemes (which didn't provide any tax revenue to my goverment) being detected or prosecuted.