From Robert E. Kelley’s Consulting: The Complete Guide to a Profitable Career:
… a loud knocking pipe created turmoil at a large nuclear plant. No one could figure out what was making the noise or how to stop it. Finally one of the engineers suggested contacting Charlie, the retired maintenance man. Charlie listened to the knocking pipe. He then followed the pipe’s course throughout the plan. After fifteen tense minutes, Charlie located a pipe connection. He asked for a large monkey wrench. Instead of using the rench to turn the pipe, he hit the pipe connection four times with the wrench. At that point, the knocking stopped. Quite relieved, the management thanked Charlie profusely. In addition, they told hime to send a bill for his services. When they received the bill, however, they were quite upset. It merely said, “For services rendered–$1,000.” They complained that the fee was exorbinant for fifteen minutes’ work. Charlie offered to send an itemized bill if they wanted one. They did. It read:
For 15 minutes' work $ 25.00 For knowing where to hit $ 975.00 TOTAL $1000.00