I'm sort of guessing here based on movies/things I have read since I ain't no money launderer, but I think locality to the source of money makes a huge difference. If you are a local drug dealer who makes all their money in their local currency in cash, then it is probably most efficient to open up some local business like a dry cleaner (i believe that's what one of the "businesses" they had in the movie american gangster) which "happens to make a bunch of money through pseudonymous cash". That way, you would only have to pay sales tax.

If you are selling to people outside your main currency though, you need someway to convert it back and "digital" transactions seem ideal so I can see the extra cost being worth it (you just happen to have a lot of american customers who like your digital product...)