More than that.
Some states have tried legalization and this is the result so far. Overall, the effect is exactly what libertarians would think.
Lower crimes (real crime now)
On the whole, crime statistics for Washington state reached a 40-year
low in 2014, with violent crime down 10 percent and a 13 percent drop
in the state’s murder rate. Colorado also saw decreases in overall
crime rates, violent crimes, and property crimes.
Teen usage drops slightly
The report was based on survey data from the state’s Department of
Health, which polled for usage among students in grades six, eight,
ten, and twelve. The results of the survey showed decreased usage by
students in all four grade levels. For example, students in the tenth
grade responded at a 17 percent usage rate in 2016, compared to rates
of 18 percent in 2006, and 20 percent in 2010.
Similar decreases in teen usage were observed in Colorado, with 21.2
percent reporting usage in 2015, down from 22 percent in 2011.
Why not wait a little longer and keep it legal than doing it now?
Even setting aside financial gains by the myriad private businesses
now operating in each state, and focusing instead on state revenues
such as excise taxes and licensing fees, the case is clear. In 2014,
Colorado received over $76 million in revenues, $35 million of which
went directly toward funding the state’s education system. In 2015,
total tax revenues from cannabis increased to over $135 million.
In Washington, $83 million was received in excise taxes alone during
the first year of recreational cannabis shops operating in the state.
In 2016 the state’s tax obligation was projected at $185 million, with
the expectation of 2017 reaching over $230 million.
The lion’s share of tax revenues in Washington are slated for public
health programs including Medicaid, substance abuse prevention, and
community health centers.
Another estimate can be seen from Silk Road. It's basically almost as good as legalization.
When both are legal, the safer drugs would sell
Marijuana was No. 1, followed by the nonspecific category "drugs." As
Christin notes in his paper, 16 of the top 20 categories are
drug-related, with "soft drugs" like marijuana outselling "hard drugs"
like opiates. "This presumably simply reflects market demand," he
So without government rules, the main advertised purpose of war on drugs, reducing harm, is already accomplished far better under free market. Consumers avoid dangerous drug and use safer drugs automatically.
Super dangerous drugs, like Flaka, don't sell. Why would anyone buy dangerous drugs if it can use safer ones with little risk of getting caught.