I came across the nugget of wisdom last night in Farmer Boy.

He waited till Father stopped talking and looked at him.
“What is it, son?” Father asked.
Almanzo was scared. “Father,” he said.
“Well, son?”
“Father,” Almanzo said, “would you–would you give me–a nickel?”
He stood there while Father and Mr. Paddock looked at him, and he
wished he could get away.
“What for?”
Almanzo looked down at his moccasins and muttered:
“Frank had a nickel. He bought pink lemonade.”
“Well,” Father said, slowly, “if Frank treated you, its’ only right
you should treat him.” Father put his hand in his pocket. Then he
stopped and asked:
“Did Frank treat you to lemonade?”
Almanzo wanted so badly to get the nickel that he nodded. Then he
squirmed and said:
“No, Father.”
Father looked at him a long time. Then took out his wallet and opened
it, and slowly he took out a round big silver half-dollar. He asked:
“Almanzo, do you know what this is?”
“Half a dollar,” Almanzo answered.
“Yes. But do you know what half a dollar is?”
Almanzo didn’t know it was anything but half a dollar.
“It’s work, son,” Father said. “That’s what money is; it’s hard work.”

……

“How much do you get for half a bushel of potatoes?”
“Half a dollar,” Almanzo said.
“Yes,” said Father. “That’s what’s in this half-dollar, Almanzo. The work that raised half a bushel of potatoes is in it.”Almanzo looked at the round piece of money that Father held up. It looked small, compared to all that work.”You can have it, Almanzo,” Father said. Almanzo could hardly believe his ears. Father gave him the heavy half dollar.”It’s yours,” said Father.  “You could buy a suckling pig with it, if you want to. You could raise it and it would raise a litter of pigs,worth four, five dollars apiece. Or you can trade that half-dollar for lemondade, and drink it up. You do as you want, it’s your money.”