it think if that happens. all the producer of illegal drugs will not be that rich tho. because of low demand about it because you can actually buy illegal drugs if it is being allowed. so disallowing it will be higher the demand of it. the higher the demand the higher the value. and it is also impossible to let illegal drugs be allowed. that why it is called illegal. if it is allowed it should be called legal.
Drug legalization will do wonders. It will mean the end of the drug cartels. Also, it would significantly reduce the number of deaths due to drug overdose, as the potency of the drug is stable. And moreover, the government can identify the addicts and enroll them to drug de-addiction programs.