Is this a theoretical restaurant or a real one? From what I understand real restaurants waste food by necessity because (for one example) mistakes are inevitable, customers are picky/mercurial, and any prepared dish that is deemed less than suitable for one customer for any reason can’t be sold to any customer.

Also equipment fails, vendors mess up, etc.

Having run a restaurant, this was not my experience.

If saving 10c costs time worth more than that then it's not worth it. Ends there, really.

A friend used to work at a known cupcake chain in London and she literally threw out 30+ cupcakes a day. Whenever I was around, I'd try to convince her not to throw them but giving the box to some homeless or random passerby. Although that wasn't a common event given the boss.

So no, many places are stupidly wasteful, sometimes because of silly legislation.

You'd need perfect forecasting to not waste food. Order exactly enough food, and serve each customer exactly what they'd eat.