Equating to 3oz./year times what, $70/oz.? $210/yr.? Given that there are 15 million marijuana users, that works out to a $3B U.S. market.
LA spends that much.
But let's go with your numbers. Make marijuana legal and the price drops 90%, bringing it in line with the cost of cigarettes. Our $3B market dropped to $300 million. "Tax the hell out of it" at 100% and that brings in $300 million.
Peanuts.
Prices would no doubt drop as big corporate growers took over and bring production costs way down. The retail price wouldn’t drop to $7 an ounce though. People will pay a lot more than that so there is no reason why it would have to go that low. They’ll probably want a lot better quality product than the crappy Mexican most smoke now, even if it’s just smoother tasting product without the seeds and stems and not so much stronger. They’ll pay a reasonable price for this. Even at today’s prices it is cheaper to smoke pot than it is to drink beer. A few puffs, far less than a gram of even standard commercial grade Mexican is enough for most people. That’s less than 1/28 of an ounce. They those who smoke the really expensive indoor grown stuff rather than cheap Mexican tend to smoke a lot less when they smoke because the stuff they get is so expensive and because it’s a lot more powerful and takes a lot less to reach the desired effect. Hardly any buy the really expensive stuff by the ounce and most aren’t buying the cheap Mexican by the ounce either. They don’t need that much pot at a time. They buy much smaller amounts like what they might smoke in a weekend or during a week, or whatever. If they were buying it at a store they might just buy a gram or two and naturally the smaller the amount people buy the more it will cost per ounce or gram. In Holland the government set the max people can buy from retail outlets at 5 grams. We might very well see similar limits here. Even without limits like that, people would likely only buy a gram or a few grams at a time and m bet is that they would be willing to pay several dollars a gram even for the lower grade product. People who buy the super expensive stuff today might pay ridiculous amounts like $30 a gram at one of those medical marijuana coops in California or on the streets. It’s incredibly expensive compared to the cost of commercial grade and those who would spend that much today for it would no doubt pay a large premium in price for the "connoisseur" stuff when it is legal. Those producing and selling it will charge what the market will bear. Look what they do with bottled water for goodness sakes.
Taxing “the hell out of it” would probably mean flat excises sort of like what we see on tobacco and not just regular sales taxes that are assessed as a percentage of the purchase price. They might have to play with the taxes some to see what the optimal excises are, but I bet if they did something like tax commercial grade under 10% THC $2 a gram, 10% to 15% THC $4 a gram, and over 15% THC $8 a gram, or some kind of taxing scheme like that, they really would bring in a fortune in tax revenues. Producers would be producing on a large scale and making plenty of profits just because of the sheer volume they would be dealing in. The product would still be cheap for consumers compared to something like beer when you think of what it costs to get whatever level of buzz you are looking for. And even high taxes like that are not likely to encourage much of a black market because clandestine grows will never be able to come close to competing to large scale commercial grows in terms of production costs. The per pound or per ounce production costs for a closet grow under lights or even one done in a whole house under lights is always going to be a whole lot higher than production costs for high grade marijuana grown in row after row of greenhouses run by big corporate farmers. Taxing it too much would encourage a big black market, but most people aren’t going to want to buy pot off the street unless they can get it for substantially less than what they pay in the store. In the store they’ll have a wide selection of good quality product grown and handled in a regulated system with safety standards. On the streets the’d be buying God knows what from people who might have used dangerous pesticides unsafe for human consumption, who could say the product is “organic” when it’s not, who could sell inferior product claiming it is a lot stronger than it is and so on. People aren’t going to have a lot of incentive to stray from the nice clean stores with nice selections of high quality relatively safe product unless the price of the street marijuana is a whole lot less than what they can get in the store and unless retail prices of legal weed after taxes are as high as they are today or higher it’s going to be hard for clandestine producers to get product to end consumers that is substantially cheaper and still make enough money to justify the risks involved.