A factory is completely shut down, costing its owner $100,000 per hour. An expert is brought in to get it up and running again. He walks around examining many machines, then pulls a screw driver out of his pocket, and adjusts one screw on one machine. The entire factory instantly starts running again.
"Thank you! Thank you! Thank you!" the plant manager exclaims, "Give me your bill."
The expert presents him with a bill for $10,000.
The plant manager, surprised by such a large bill for so little effort, asked for an itemized bill.
The itemized bill:
Turning a screw: $1
Knowing which screw to turn: $9,999