That didn't work for legal medical marijuana in California.
Doesn't apply ... it's illegal to sell medical marijuana in California.
That didn't work for government supplied legal medical marijuana in Canada.
Doesn't apply ... availability was unchanged for nonmedical users, who vastly outnumber medical users.
That didn't work for legal recreational marijuana in Amsterdam.
Doesn't apply ... it's still illegal to grow it there.
Real conservatives know that when supply and demand is claimed to not work, as liberals love to claim, the whole story is not being told.
You wouldn't know it by the number of stores opening up -- in plain view of public officials and the police. Why should the medical marijuana from these stores cost more than black market? They legally grow their own for pennies.
"... availability was unchanged for nonmedical users, who vastly outnumber medical users."
So what? You must be a registered patient to buy medical marijuana in Canada. Why isn't medical marijuana cheap for those few who are authorized to buy it?
"it's still illegal to grow it there."
Then certainly you can refer me to a news story which announces a marijuana bust in Amsterdam.
Legal marijuana is actually more expensive in the above instances than black market. You have no basis to assume it will be cheaper. None.