Lesson Failed

Over the summer, I tried to teach Zach his first lesson in money - how to spend it, what it's worth. There was a neighborhood yard sale a block away, so John and I decided to take the kids there to check it out - the neighbors, their junk, and just have a nice time outside in the summer sun. I gave Zach and Asia each a quarter and said that they could use it to buy something at the yard sale. Both put their money in their pockets for safe-keeping. In the meantime, Zach managed to find two dimes laying around the house and added them to his stash.
We drove to the yard sale since we were going to explore more of Pittsburgh downtown after the yard sale. The first yard we looked at didn't have any kids things. Mostly hunting things and a really expensive old trunk. I thought it could be a good toy chest, but it cost something like 20 dollars or more. I couldn't see what was so special with that trunk. The next few houses had lots of kids things. Asia and I stayed at those houses for awhile, looking at the dolls and books. Zach and John went ahead to another house down the street. Asia managed to get a magic wand and two Barbie dolls for 20 cents. I also bought some half-used workbooks for Zach. A little girl ran into her house showing the money she made- about a dollar. I could hear her brother telling her she had to share the money. They were really excited about earning that dollar. Meanwhile, Asia had succeeded in her first money lesson.
Zach, on the other hand, had lost all his money! The dimes had slipped out of his pockets or hands or something. I think I even found one of the dimes in the toy box where Asia and I had bought the dolls. I gave it to the little girl who was selling her stuff. Zach lost his quarter because he found this big plastic car and thought it was a ride! He put his quarter in a hole in the car. We shook the car and could hear the quarter clunking around inside. So Zach failed his lesson. Asia shared her magic wand with him, so he was happy. He also said that we could go home at any time and get more money. He didn't think it was a big deal. A miserable failure there. Oh well.
But I wonder, is he too young to grasp the concept of money or is it that he sees how loose we are with money and thinks it's readily available to use or lose whenever he wants? Maybe I'm just being paranoid and overanalyzing. That's what Mom's do, you know.