There are a lot of reasons that I don't want the money I spend on cannabis to go to the illicit market. The biggest is that illicit traffickers and violence go hand in hand. I would much rather give my money to local farmers any day - and I'm not alone it seems.
Really interesting story over at Hightimes on some studies that have examined the impact of cannabis legalization on the illicit market.
According to Jonathan Rubin, CEO of New Leaf Data Services
While legal cannabis will nearly always incur higher productions costs due to regulatory compliance (from testing and packaging requirements to license fees and taxes), the dramatic price erosion witnessed over the past few years makes legal supplies more price competitive with the black market.
As you read the article, you'll see that its not a straight forward calculation since its based on indirect observations, like the number of seizures. A major factor that impacts those observations is that cops simply aren't looking for weed busts in legal states, so there are fewer seizures. So, no matter what the data is actually saying, the important part is that cops aren't busting people for farming and trading in cannabis.