When I was very young I assumed adults bought money at stores. Since money was the only means which I knew of to make purchases, I deduced they bought money with money at a 1:1 ratio, which made no sense even then but seemed like the only rational possibility
A childhood belief about money

others believed things like this
- When I was a little kid I used to believe that tissue paper was money and that you could have a box of money.Anon
- I used to belive that if you went up to an ATM it would just give you money out that is not your own money.Anon
- when I was little I believed that if I put a white stone under the pillow with my tooth I make more moneyAnon
- I used to believe that you had to "buy" your job. The more money you paid, the better the job. — Duke
- When I was kid I used to believe that I had to earn enough money to have one of everything that existed.Anon
- I used to think that money from ATM machines were free :p— qwerty