story supposedly goes something like this:
One of Ford's factory machines was making a terrible noise. he hired a consultant to fix it. The guy came listened to the machine for a few minutes, then drew on on of the pipes with a piece of chalk, told them to replace that one.
Send Ford a bill for 10,000$. Mr. Ford refused to pay that much, and demanded a breakdown.
The consultant sent back:
Time: 95$
Chalk: 5$
Knowing where to make the mark: 9,900$