Generally guys like this are factored into the business plan, but sometimes people try to outsmart (or in this case outeat) the restaurant.
I remember reading once that crab legs were often a loss leader food. The restaurant offered crab legs to pull people in despite being too expensive for the buffet. Most people ate a few and then filled up on cheaper foods. Some people however would just eat crab legs.
I remember another example of this where a customer stayed from lunch until dinner. Not only did lunch cost less, but now that's two meals. The fix there was a three hour table limit. Basically affects no one, except the exceptions.