It's dubious at best to think that we would make a profit from taxes on weed. I did a bunch of research after Tom Ammiano introduced AB 390 into the state legis. here in California (which became Prop 19 on the ballot) for my county's Libertarian Party. What I found was interesting.
The state's Board of Equalization (in charge of collecting all tax revenue) did a bunch of studies on the viability of taxation for profit. They assumed that marijuana usage would closely mimic alcohol and tobacco consumption and regulation. For alcohol/tobacco tax revenues, the state pulled in about $4.4 billion in 2008 (the last year that current data is available) but the state also spent more than $19 billion on programs and healthcare costs aimed at alleviating the potential fallout from alcohol/tobacco abuse.
There's no reason to think that this won't also be the case with weed. Plus, if you read the language of the bill, there is no bureaucracy whatsoever set up to ensure that tax dollars are collected, aside from what's already in place. Think about it: the bill would have allowed me to grow weed in my home. But how is the govt going to collect taxes from me? How are they going to get a piece of the pie everytime I flip an ounce to my neighbor across the street? They can't. They can tax collectives and dispensaries, but those places will transfer the cost onto the consumer. Private citizens can circumvent this added cost by simply growing it themselves. It's not that hard to grow some extremely potent weed if you get some decent clones. I've done it a bunch of times and the weed I've grown is at least as good as anything at a cannabis club, outside of the shit that's so expensive it's priced way above the common street price.
Of course, then you have the societal obligation aspect to this whole thing. Weed is not dangerous on the level of cocaine or heroin or alcohol, but it is dangerous and carries the potential for addiction. Regardless of what anyone says, it is very much a gateway drug. My own personal experiences, along with those of EVERYONE I know who smoked(s) weed regularly backs this assertion up. If the govt were to legalize weed, they would necessarily bear the responsibility to provide programs similar to the ones already in place for alcohol/tobacco abuse.
The fastest-growing abused drug amongst teenagers are pharmaceutical painkillers and psychotherapeutic drugs such as Ritalin or Vicodine. There are endless studies demonstrating the immense negative impact that the combination of any hallucinogen or depressant and these pharmaceutical drugs can have, especially on the still-developing brains of teenagers. So marijuana is indeed dangerous to a certain extent. Is the govt really prepared to legalize something, create a market for it with the intention of making a profit, and then turn around and discourage people from ever entering that market in the first place? I think not.
I support legalization, but I voted against Prop 19. To me the tax money is nothing more than blood money. As a Libertarian, I am loathe to let the govt determine what I can and can't put into my own body. But I'm even more loathe to let the govt tax and regulate something that I can pretty much already use anyways. I would only support legalization if it meant that weed became legal and forgotten about. No taxing of it, no regulating of it.
This post is getting long, so I won't go into the details here, but the Board of Equalization also determined that there is no reason to think that weed consumption won't go up significantly or that weed prices will go down if it is legalized.