The only way the Fair Tax will bring in more money from this group is if this group collects and forwards the Fair Tax on their goods and services.
For example, the drug dealer will have to add 30% to his drug prices and forward that money to the government. Ditto the prostitute.
Now, they don't file a 1040 today. I doubt they'll register a collect the Fair Tax tomorrow.
I operate under no illusion that the drug dealer or prostitute will collect tax. But when they take the profits of their ill-gotten gain to Wal-mart, it will be taxed.