Effort or no effort?

A giant ship engine failed. The ship's owners tried one expert after
another, but none of them could figure but how to fix the engine. Then they
brought in an old man who had been fixing ships since he was a young. He
carried a large bag of tools with him, and when he arrived, he immediately
went to work. He inspected the engine very carefully, top to bottom.

 Two of the ship's owners were there, watching this man, hoping he would
know what to do. After looking things over, the old man reached into his bag
and pulled out a small hammer. He gently tapped something. Instantly, the
engine lurched into life. He carefully put his hammer away.

 The engine was fixed! A week later, the owners received a bill from the
old man for ten thousand dollars. "What?!" the owners exclaimed. "He hardly
did anything!" So they wrote the old man a note saying, "Please send us an
itemized bill."

 The man sent a bill that read:

 Tapping with a hammer......................... $     2.00
 Knowing where to tap.......................... $ 9,998.00

Effort is important, but knowing where to make an effort makes all the difference