I'm not so sure about that, TBH; in fact, I'd suspect that it'd be the other way around(at least in the Americas, anyway); you could get the cheap-ass mass produced store bought stuff(that's probably full of chemicals and had all the good stuff taken out of it!), but unless you're on a real tight budget, why bother with that crap when you could get a better organic product, or even grow and roll the stuff yourself for just a little bit more, and without any real risk of lung cancer down the line(while enjoying an actual high, too)?
My answer to this is the following question: What percentage of alcohol drinkers and cigarette smokers do you think actually produce themselves what they consume ? Sure pot isn't the hardest thing to grow but people are lazy by nature and I doubt most people would have the place for enough plants to sustain an habit.