The cheapest things I do cannot compare with the cheapest thing that my 16-year-old son does.
When we take the family to the local baseball games, we give each of the kids $10 to spend on food (so that they don't endlessly pester us). This kid waits for his two siblings to buy more food than they need, and when they get full, he downs their leftovers and goes home with the $10 still in his pocket.
I think when I'm old and gray I'm gonna hit him up for loans. Somehow I just KNOW he will have money.