If the government saved a ton of money by not trying to fight the "War on Drugs" and also collected a lot of tax revenue on softer drugs like marijuana they'd have a lot more to put into education, treatment and prevention.
The last figure that I read was that 85% of the DEA's budget was spent fighting marijuana.
If it were legalized, overnight, that would mean that the amount of money available to go after cocaine, heroin, crystal meth and prescription opiate trafficking would be increased by about 566%.