Door frames

Selling door frames must be one of the hardest jobs in the world. Think about it a second. You're mainly selling an empty void where the door goes. I suppose, if someone actually is in the market for purchasing a door frame then they really do need it and they'll buy it anyway. Still, how do you market something like that? The market has to be just as big as the door market (from a logical point of view) and you see those advertised far more often. Tell you what, I'll sell you as much empty sky as you want for a grand. Any takers?