A pipe burst in a doctor's house.

A pipe burst in a doctor's house.
He called a plumber.
The plumber arrived, unpacked his tools, did mysterious plumber-type things for a while, and handed the doctor a bill for $600.
The doctor exclaimed, "This is ridiculous!
I don't even make that much as a doctor!
." The plumber quietly answered, "Neither did I when I was a doctor."