First, there are about 22 grams of tobacco in a typical pack of cigarettes. At the $11 per 2.5 grams price you quoted in your message, it would cost nearly $100 for a pack of legal marijuana with as much marijuana in it as a typical pack of cigarettes... with (again using your estimate) about $87 of that amount being tax -- tax that could go towards operational expenses and profit of a black market enterprise that could provide tax-free marijuana.
Second, cigarette smuggling does exist, and organized crime is heavily involved in it.[1]
Third, (as demonstrated in the above) legal marijuana does not have to cost as much as the current price of illegal marijuana to make a black market viable. It just has to cost enough to make the trouble of buying marijuana on the black market seem worthwhile for the consumer and the profit and risk worthwhile to the dealers. We can call this the "black market viability price point".
It's quite likely that this black market viability price point can be significantly below current illegal marijuana prices. But it's not yet clear how much above the cost of production legal marijuana can be taxed before it approaches the black market viability price point.
Alcohol legalization and taxation might be seen as a positive role model for how marijuana legalization and taxation could be carried out. Alcohol is now legal and taxed, but there isn't much (any?) of market for black market alcohol in the US.
Second, cigarette smuggling does exist, and organized crime is heavily involved in it.[1]
Third, (as demonstrated in the above) legal marijuana does not have to cost as much as the current price of illegal marijuana to make a black market viable. It just has to cost enough to make the trouble of buying marijuana on the black market seem worthwhile for the consumer and the profit and risk worthwhile to the dealers. We can call this the "black market viability price point".
It's quite likely that this black market viability price point can be significantly below current illegal marijuana prices. But it's not yet clear how much above the cost of production legal marijuana can be taxed before it approaches the black market viability price point.
Alcohol legalization and taxation might be seen as a positive role model for how marijuana legalization and taxation could be carried out. Alcohol is now legal and taxed, but there isn't much (any?) of market for black market alcohol in the US.
[1] - https://en.wikipedia.org/wiki/Cigarette_smuggling