Really hard to profit on something so easy to grow its called a weed. If decriminalized I dont see a large trade in store-bought pot. Some for the connoisseurs who want a different type of bud.
For the most part those who want to partake regularly will likely try growing one female plant and harvestign the buds as they mature.
In any case it will remove the profit potential that feeds the black marketeers.
So drug dealers will get out of the cocaine, meth, crack, acid, x, xanex, etc markets if pot is legalized? I doubt it.
Tobacco grows like a weed. Alcohol ferments naturally in rotting fruit. Nonetheless, purveyors of both products have made billions from selling them. Americans are lazy. Just as most of us don't grow our own tobacco and brew our own beer, many will gladly pay for a mass-produced marijuana product.
If it is taxed, growing your own will be illegal (especially if you are selling it). DEA agents will become BATFEC (C for cannabis) agents and will hound bootleggers mercilessly. Because of WOsD the mechanism is in place.
It's easy to distill booze, too, but few get involved with it for long due to BATFE diligence. Oh there may be some kitchen whisky made, but as soon as you get up to making several gallons a whack on a regular basis, they'll be looking for you just as if you had 20 metal halide lamps in your basement.
If it's so hard to profit, why are there Mexican drug lords with armies?
And as I said above "decriminalize" is not "legalize".