Legal cannabis will naturally be much, much cheaper than illegal cannabis. A joint is the same sort of item as a teabag: the dried flowers of a plant in a wrapper. A fancy teabag costs a dime at the supermarket; the marijuana in an average joint costs about $4 (0.4 gram of sinsemilla flowers @ $10/gram) on the current illicit and quasi-medical markets. The combination of not having to worry about law enforcement and the economies of mass production will inevitably drive the joint price down close to the teabag price. (Generic tobacco cigarettes can be manufactured for about two cents each; the remainder of the price is marketing expense, quasi-rent on brand names, and taxes.)