"Starting with a tobacco seed, and eventually producing a cigarette, is hard. That is why PM makes money, and the product is so heavily taxed.
Starting with a MJ seed, and eventually producing a joint, is so easy that stoned people do it it all the time.
So...how are you going to tax it?"
What makes you think it's so much harder to produce dried and cured tobacco than it is to produce dried and cured marijuana? People aren't going to want to grow their own pot anymore than their going to want to grow their own tobacco or brew their own beer. It takes time and money, requires growing space, gardening skills, knowledge about the process, and lot's of work to grow high quality marijuana. Most people won't have the growing space or be ambitious enough to learn the skills and do all the work involved. For most it will be like it is for those like me who have brewed beer, something people do once or twice and never again because they realize how much of a pain in the neck it is and how it isn't nearly as easy as it sounds like it is going to be to get good results. Most who smoke pot don't even need nearly as much as they would get in a crop anyway. Most would be just tickled to death if they could pop on down to a licensed shop and select from a wide variety of product on the shelves. Commercial growers would be able to produce consistent smooth smoking high quality product with tastes and aromas pot smokers appreciate and pretty soon people would have favorite varieties or brands that they stick with, and they'll have no more interest in homegrown some yahoo grew in his back yard than they down in homebrew some yahoo brewed in his closet. Production costs could be much lower if the product was mass produced with modern agricultural methods and overall costs would be lower without all the middle men and risks currently involved in bringing the product to consumers. There would be a lot of room for tax without encouraging a black market.
I've been told that marijuana is a weed that grows everywhere. Now you come along and tell me that me it's just as difficult as tobacco. I guess the side of the fence you're on depends on the argument you wish to make, huh?
"People aren't going to want to grow their own pot"
You can't possibly know that. Number one, they're already growing their own pot today (how many are growing their own tobacco?).
Secondly, you don't know how much legal pot will cost, or the amount of taxes imposed. Tax it like tobacco, and we'll see a continuance of the black market.
Third, the government, as part of its legalization concession, may limit the THC content. They've discussed doing that with the nicotine content of tobacco, so it's possible.
Fourth, what will be the legal age for marijuana? Again, as a concession to legalization, the legal age could be set at 23 or 25.
There are a number of scenarios that are conducive to people growing their own. I wouldn't dismiss that possibility so flippantly.