Here in Austin there are several buffet places. There are the Chinese food buffet’s that serve all-you-can-eat Chinese food, and places like Sirloin Stockade that generally serve all-you-can-eat American type food (except there’s no hot dogs or hamburgers). These places generally charge by person and age, so kids under 12 pay less than an adult. They aren’t especially cheap, but the beauty of it is that you can eat like a heifer until you feel as if you’ve gotten your money’s worth.
There’s been some drawbacks due to this type of business model. For instance, in Houma, Louisiana, two large gentlemen were reportedly kicked out of a Chinese buffet because they were eating too much. Another incident had to do with parents being upset because they were paying by their kids height rather than their age.
Obviously the thing to do is to pay by weight. Weigh people when they come in, weigh them when they leave, and charge them the difference. The only drawback I could see to that is the bathrooms. It’s against to law to close them off, but you’d still have to worry about people who purge, at either end.