A doctor is walking down the street and sees a store sign that says
BRAINS FOR SALE. So he walks in.

He says, "How much is a doctor's brain?"

The man says, "$100 bucks."

The doctor says, "How much is a nurse's brain?"

The man says, "$500 bucks."

The doctor says, "How much is a lawyer's brain?"

The man says, "$1000 bucks."

The doctor asks, "Why is the lawyer's brain so much?"

The man says, "Because it's never been used!"