Henry Ford had ordered a dynamo for one of his plants. The dynamo didn't work, and not even the manufacturers could figure out why. A Ford employee told his boss that Von Neumann was "the smartest man in America," so Ford called Von Neumann and asked him to come out and take a look at the dynamo.
Von Neumann came, looked at the schematics, walked around the dynamo,
then took out a pencil.
He marked a line on the outside casing and said, "If you'll go in an cut the coil here, the dynamo will work fine."
They cut the coil, and the dynamo did work fine.
Ford then told Von Neumann to send him a bill for the work. Von Neumann sent Ford a bill for $5,000.
Ford was astounded -- $5,000 was a lot in the 1950s -- and asked Von Neumann for an itemized account.
Here's what he submitted:
Drawing a line with the pencil: $ 1
Knowing where to draw the line with the pencil: $4,999
Ford paid the bill.