Meth is very cheap already. Any changes?
I think it would end up more expensive at your local pharmacy if legalized. The benefit would be you know you won't lose your teeth from the odd chemicals the producer is using.
(I could be horribly off on the details)
Methamphetamine is currently available at your local pharmacy. It's a generic drugs and costs less than a $1 per dose.
You don't lose your teeth from meth because of chemicals used in it's production, you lose them due to a combination of poor oral hygiene and reduced saliva production. The same thing happens if you abuse the stuff you can get at the pharmacy.