There is a huge wildcard in that math equation -- the federal government.
Supporters of legalizing marijuana for recreational use have been pointing out the financial benefits for state and local governments. While the initiative doesn't spell out how much they could earn, it leaves the door open to taxing the drug.
Assemblyman Tom Ammiano, D-San Francisco, had been championing a similar proposal through the Legislature.
"Excise taxes and sales tax, and the estimate from that is $1.5 billion," he said.
In these tight budgetary times, the money is tempting.
Supporters say decriminalizing pot would save tens of millions in prison and law enforcement costs. And new taxes would help California's deficit-plagued finances.
"All those programs to teach kids about drugs, to de-mystify it, why it's bad -- all those have been cut, so then we can replenish those programs because they are effective," Ammiano.
But law enforcement says the social ills outweigh the money gained.
"We already have significant problems with alcohol. We have significant problems with pharmaceuticals. We tax them both, but, in fact, the cost to our society is much greater than the revenue we bring in," John Lovell from the California Police Chiefs Association said.
If the marijuana initiative passes, the other problem is it conflicts with federal law, which would still treat marijuana possession as a crime.
"It doesn't make California citizens immune from the application of the federal law. They could still get arrested and prosecuted," University of the Pacific, McGeorge School of Law professor Leslie Jacobs said.
For 15 states like California that have medical marijuana, U.S. Attorney General Eric Holder announced last fall raiding dispensaries would be a low priority. There's no guarantee, though, the same policy would apply under legalized recreational use.
The marijuana initiative will probably be one of the most watched campaigns this November because there's a national debate over whether it's time to soften drug laws.