When my son was between 8-10 years old, he went to visit his grandparents on his own.  He went to a parade and got candy and then was selling it to employees at my parent's business.  When he got home he told me he thought he had made a mistake.  His dollars were depreciating and he should have asked for payment in gold or silver.  

I don't think he would've gotten anyone to buy a candy bar with gold or silver, but it still made my heart swell with pride.