Stopping it in the first place would be great! Unfortunately, leaving addicts (and their families) pennyless doesn't seem to be working. Currently, our drug (and DUI) laws are basically cash cows for the state with very few judges looking favorably upon drug/alcohol treatment until someone has multiple offenses or worse. Of course, I can only speak from what I know from working with addicts/alcoholics in this area.
I wish I knew the answer... but I have to say that what we are doing doesn't seem to be working.
Here in Florida we have a Drug Court program. Users are court-ordered to treatment, as opposed to jail. Costs very little but since it is court ordered, and if they resue, they go to jail, it works very well.. and is very inexpensive.