Does that make you smart? You're trading pussy for weed. Weed is less valuable. So you're taking the loss on the trade. If you're willing to whore yourself out for some weed, why shouldn't he take advantage.
If you would have sex with him anyway, and the marijuana is just a bonus then it seems ok...I suppose.
think about this. how many girls seduce men for free drinks at the bar. what you're doing, i would say, is better