I second this. My parents set up a notebook in their office that was my running checking account. Whenever I got a birthday check or earned some money, they would cash it in their own account and credit the value. Whenever I wanted to buy a toy, they would deduct the value. (You were lucky that you got compounded interest, though! My parental account had a zero interest rate.)

At the age of 10 I was acutely aware of the value of things and more concerned with keeping the balance on my imaginary account high than with having every toy or computer game I could see. To this day I don't like buying "stuff". It was an awesome parenting move.