Along with the disassembly of your point made by others, I'd observe that your argument falls flat even before we get to the question of wine. Bulk MJ is much more like oregano in the processing and creation than a wine process; its mind altering-ness hardly factors into costs of production at all.
I think you may be making a critical, but easy, economic error, which is considering only one side of the supply/demand dynamic. Yes, demand may be sky high, but that only implies high prices if supply is scarce. Things with sky-high demand and a corresponding sky-high supply are still frequently very, very cheap. And legal MJ's supply would be sky high; as others have pointed out, it's called "weed" for a reason. It is not hard to grow, it is not hard to process, it is not hard to move, it doesn't take specialized equipment beyond what already exists off the shelf. The only two ways for the price to end up even remotely high is for the government to tax the hell out of it, or for a cartel to form. And it's very difficult to see how a cartel could form under those circumstances, too; how would you form a dandelion cartel?
I think you may be making a critical, but easy, economic error, which is considering only one side of the supply/demand dynamic. Yes, demand may be sky high, but that only implies high prices if supply is scarce. Things with sky-high demand and a corresponding sky-high supply are still frequently very, very cheap. And legal MJ's supply would be sky high; as others have pointed out, it's called "weed" for a reason. It is not hard to grow, it is not hard to process, it is not hard to move, it doesn't take specialized equipment beyond what already exists off the shelf. The only two ways for the price to end up even remotely high is for the government to tax the hell out of it, or for a cartel to form. And it's very difficult to see how a cartel could form under those circumstances, too; how would you form a dandelion cartel?