Nonsense - risk is gone but competition explodes so price plummets, as it did with the end of Prohibition ... Econ 101.
Those that control the distribution reap profits without risk of conflict with law enforcement. The price goes down but the profits go up because the cost of delivery is brought down.
Therefore with legalization the drug lords win because they retain the profits and eliminate the high cost of delivery. They could care less whether price falls so long as their profits are up.
Try again and be sure to review your Econ 101 notes or try and finish that class that you either dropped out of or failed.