When my son was 8-10, he went to visit his grandparents. They went to a parade and he got candy. He then went to work with them (they owned their business before they retired). He was selling candy. He then came to us with concern because he said his money was being inflated away. He asked if he should only accept payment in gold or silver.

Although I told him nobody would buy it if he required payment in gold or silver, I was kind of proud of him for understanding money better than most adults.