A mainframe computer on which everyone in the office depended suddenly went down.

They tried everything but it still wouldnt work. Finally they decided to call in a high-powered computer consultant.

He arrived, looked at the computer, took out a small hammer and tapped it on the side. Instantly the computer leapt back to life.
Two days later the office manager received a bill from the consultant for $1,000.

Immediately he called the consultant and exclaimed, One thousand
dollars for fixing that computer?! You were only here five minutes! I want the bill itemized!

The next day the new bill arrived. It read,

Tapping computer with hammer: $1
Knowing where to tap: $999