What goes under the pot..... Means the things that fall out of the pot or never make it to the pot. Those things are most costly because, either they are too big to fit in the pot so they cost more. Now what goes inside is much smaller so less costly.... Unless we are talking about the GoLd and valuble things. So what goes under the pot is big.. and what does inside small... And cost as much...... If you asked it as a joke.
Real meaning: The first would that goes to cook the food in the pot is much costly that the raw food that goes inside the pot. COst of fuel>cost of food.... Thats all