The largest post-prison program is drug rehab.
Drug rehab after prison?

Yep, people get enough drugs in prison to become addicted.

And, to properly think about this, the number of people using any drug in a city... what is the quantity they are using?

All the cop shows show drug deals with a suitcase of drugs.
This is false.
THINK, SEMI-TRUCK FULLS EVERY DAY.

Think of all the people that have to be in on it for a semi-truck to drive into a city every day.

Drugs are big business. Last year the cops "stole" more money from people than the amount of theft reported from burglary.