Freakonomics hit it on the head.
Take out supplier - supply dwindles, price goes up and it becomes economically enticing for someone to step in and become a new supplier (new dealer/cartel etc)
If you simply locked up every user or executed them immediately - make USING (demand) so reprehensible that to do so is an instant death sentence or locked away for life - zero tolerance (not advocating that - simply applying it as example) - the demand drops, price drops. Economic incentive to produce/deal goes away and suppliers walk away from the market. Like I'm sure any other industry when demand drops.
