To the writers of The Cabin In the Woods

I am totally baffled by this film. I understand the entire tongue in cheek caricature of the horror genre as a whole. I understand the clever joke of having the most typical characters spend a weekend partying in a cabin  in the woods. I get metafiction. But I don't understand how the people who wrote this film could come up with such a clever premise for a film, attract legitimate stars and make a pretty well made film but create such completely cheesy dialogue. "I'm living in a world of reefer!" Are you serious?