The bucks of food

Maybe someone with a better grounding in economics can explain this one to me...

We've all been at a restaurant, ordering, say, a bowl of Cafe Asia's delicious fried rice, which only costs about 8 dollars. The dish comes out and your first reaction is one of absolute horror. It's HUGE. You think you might have to put on some climbing gear to get to the top of it. You wonder if they made a mistake and thought you asked for "The Gutbuster". You wonder if your recent slight weight gain was noticed by the kitchen staff who thought, "He's a hungry boy. Give him double."

But what I wonder is this: Couldn't the kitchen cut the portion by at least a quarter, still giving the patron an American-sized amount of food, but still charge the same? It would still be a huge portion, enough for two meals, and I can't imagine anyone would look at it and think, "That's what my eight dollars gives me?!" They would still tuck in without thinking about it, be stuffed at the end, and the restaurant would profit off of using less food. Not nearly as much food gets wasted, the customer isn't over-fed, and the restaurant makes more money. Who doesn't this benefit?!

See? This is the shit I think about.