An old engineer retires. A year or so later, the firm calls him up. They are having a technical issue with a machine he designed. No one else in the company can figure out what's wrong and they want him to help. He aggrees and comes in. He walks up to the machine, opens a panel, and stares into the workings. After a while, he pulls a piece of chalk out of his pocket and scribes an "X" on one particular component. He says, "There's your problem." and leaves. Sure enough, the firm replaces that part and everything is working fine. A few days later, the firm receives a bill from the retired engineer for $100,000. They call him, asking why the bill is so outrageous. He replies, itemizing the bill, "It's $1 for chalk and $99,999 for knowing where to put it."