Ever since states have started to legalize marijuana , people have debated the effects of legalization. Well, here's one consequence: Weed has gotten cheaper in Washington since the state legalized it.According to an analysis of data from the Washington’s Liquor and Cannabis Board, the price of pot has gone down by about two percent per month. Steve Davenport, a doctoral candidate at the Pardee RAND Graduate School who conducted the research, told The Washington Post that if the trend continues, the cost should fall by about 25 percent per year.This shouldn't come as a surprise given the basic laws of supply and demand. Due to the lifting of legal obstacles, the supply of weed is more abundant, so the value has gone down.“It’s just a plant," Jonathan Caulkins, a professor at Carnegie Mellon University who also conducted the research, told the Post. So, once it's widely available, there's no reason is should cost more than any other produce. "There will always be the marijuana equivalent of organically grown specialty crops sold at premium prices to yuppies," he said, "but at the same time, no-frills generic forms could become cheap enough to give away as a loss leader — the way bars give patrons beer nuts and hotels leave chocolates on your pillow.”We're not yet at the point where cannabis is as commonplace as chocolate, but we could be getting there soon. It's legal for recreational use in four states and Washington, D.C., and 20 additional states allow it for medical purposes. California will vote on a measure to legalize it recreationally in November.