(Written in response to something I read advocating the creation of drug treatment programs in prison, and using the justification of cost effectivness. You know, "spend the cash now, and get the payback later".)
Try some other math (and this is coming from a person who served 8 years in federal prison, so the subject is not as foreign to me as your writing shows that it still is to you). Legal drugs are so cheap that no one has to commit any crime to be able to afford them. Legalize everything and don't spend the money on rehab or prison, and see how much the savings are then.
William Burroughs, The Naked Lunch, addicts who have cheap high quality and plentiful drugs can often just do their thing and still be "productive members of society". Besides, you don't go around rousting up street winos and trying to force them to move to a better place in their lives, do you?
Don't get me wrong. I completely respect where you're coming from, even if you don't have a clue what you're talking about. Wrap your mind around this thought though; it will take no more effort to achieve full drug legalization than it will take to achieve decent prison reform, and society will benefit far more from keeping millions of us out of prison in the first place than it will from building a whole shitload of nicer prisons for us to do our time in. For the most part voters just plain don't want to be bothered with the whole subject of prison conditions, just like they don't want to have to think about why we're still doing the same old drug war thing that hasn't made a lick of sense since day one. If insanity is doing the same failed thing over and over, most of us feel better being a bit crazy in this area as long as it means really never having to confront our ongoing mistake.
Please, take on the legalization challenge, because the task isn't any harder and the ultimate payoff is magnitudes greater than trying to figure out a way to make everyone decide that they no longer have any desire for mind altering substances.