The tax revenue is what will eventually make the change.
The more prevalent that legalized pot becomes, the more the price will drop. There will be no revenue on marijuana when it is grown by the quarter section and planted by John Deeres and not aging pony-tailed hippies on patios. The price will be slightly less than that of good alfalfa hay...so figure the government's share of $150 a ton...
Dude, do you math much?
I don't think you understand how taxes on things like tobacco and alcohol work. Legalizing micro breweries didn't make beer unprofitable, and gov's pull plenty of taxes on alcohol. Regardless if there is some price drop on the low end weed(high end stuff will remain much more expensive), govs still will be pulling millions in taxes.
Add the benefit of not expending money in policing, prosecuting, and jailing people for weed. To say nothing of the crime decrease that has accompanied legalization.