In the Count of Monte Cristo, our young protagonist decides to use his down time to train. He sharpens his mind *and his body. He studies different disciplines and, in this particular scene, he gives the definition of economics.
Thanks to Adrian Fohr for the clip and the description!
I had seen the movie a couple of times as a youngster and that time, details such as this one, had passed me by without notice. However, working in the minerals exploration and mining industry the quote came back to my memory! What a brilliantly concise and appropriate definition!