The price is already dropping, according to a couple of my marijuana growing neighbors. Some of their crop, which they were able to tumble off and sell before, is no longer marketable due to excessive supply. The higher priced stuff (buds?) are selling for much less.
Yes, the price of cannabis did drop when a bunch of states legalized it.
The people who are growing in the non-legal states have to compete with the people who are growing “en masse” and shipping the overflow that is left after local demand is left at a lower rate.
The black market price has dropped from it’s heyday where an ounce would sell to an end user for about 300 an ounce to about 200 an ounce, or about 2500 a pound. The legal price of an ounce is around 300 (including the very high taxes) so the black market numbers in the areas where it is legal will be under that; in urban areas like NYC where it is illegal the prices can go as high as 400-500.
As the industry spreads, it will bring a bunch of new jobs and even careers with it. It is one of the fastest growing cottage industries in the US.