Don't ever underestimate experience

A ship engine failed and no one could fix it, so they brought in a guy with 40 years experience.

 
He inspected the engine very carefully, top to bottom.

 
After looking things over, the guy reached into his bag and pulled out a small hammer.

 
He gently tapped something. Instantly, the engine burst back into life.

 
The engine was fixed!

 
7 Days later the owners got his bill for $10,000.

 
"What?!" the owners said. "You hardly did anything. Send us an itemized bill."

 
The reply simply said:

• Tapping with a hammer: $2
• Knowing where to tap: $9,998