Even with a punishing tax rate, a sack of legal weed would still cost far less than the current black market prices. I suspect those inclined would happily pay a big tax to fire up their bongs legally.
And growing pot is a pain, especially for a recreational user. Why have home brew kits not driven Budweiser out of business, and why do bags of tobacco not outsell cigarettes? Again, people will gladly pay the tax for (1) convenience and (2) peace of mind in being legal.
True, but what about all of those violent Mexican drug gangs? What are they going to do for gainful employment?