What you left out of this equation is your personal motivation to see your efforts through to completion....everyone simply does not posess similar motivation, dextarity and fiskar prices being equal with others.
You are still seeing things through the looking glass of how things are today.
Ever hear of Bush Beans? It's a large company that makes a lot of canned food, most famous for baked beans.
They own thousands of acres of land where they grow produce, and buy produce from others and can it.
This is highly different process than growing a few bean plants in your back yard and making great home grown beans.
Suppose weed is fully legal, although regulated. Is fucking growing everywhere. I'll bet that the "grow your own" movement almost dies out. Percentage wise, very few people grow any of the food they eat, or products they consume, although they could.
A lot of people have a garden, but still buy many of the other things they eat.
Weed will be like this. Why go through the pain in the ass of growing if you can buy great weed like cigarette and beer?
Most people will stop. There won't be any money in it anymore.
A very large company, like bush beans, will come in, grow an ass load, hire all the work done for super cheap, and sell really good weed for cheap.
The variety of strains will go way down, as there isn't that much difference in the ones I've tried outside of the sativa or indica options. Smell might be a little different, as well as some visual aspects, but the high feels mostly the same.
If nation wide prohibition is lifted and you think you will still be able to grow weed for a profit, your living in a dream.
Colorado is a poor example, though legal there, those wishing to supply their stores still have to compete with buyers in other parts of the country for the same goods.
While it is still illegal federally, no major investment is going to take place. By major I mean hundreds of millions or billions that will be invested once all illegalities are removed.
You may grow your own weed in the same sense that my dad grows his own tomatoes and onions... A hobby.
If you're lucky, you might have a recognizable name or something some corporation finds valuable. They might offer you some money and/or a position with them for the rights to your brand or whatever they want.