A pan may be a fixed expense but it is to a significant-extend used up at the rate that people consume food, so it's not really "free" if fewer people are in the restaurant. Only "rent rent" and wages if fewer people in the restaurant.

Essentially, economies of scale might be possible in operating a restaurant but the place would need to be organized for this from the beginning - the simple ability to get people in the door is worth less than a large share of the receipts.