It's kind of funny if he's really annoying, but I think at this point just telling him to leave you alone is a better bet.

Do not, I repeat, DO NOT cheat him out of his hard-earned money for weed. In fact, if you sell him good weed at a decent price, and he show's all of his newbie friends, you have just cornered and monopolized yourself your own private market share-- well worth it, IMO.