Cardiologist vs. Mechanic

A motor mechanic was removing a cylinder head from the motor of a
BMW M3 when he spotted a well-known cardiologist in his shop.
The cardiologist was there waiting for the service manager to come
and take a look at his car when the mechanic shouted across the
garage, “Hey Doc, want to take a look at this?” The cardiologist,
a bit surprised walked over to where the mechanic was working on the
BMW.
The mechanic straightened up, wiped his hands on a rag and asked,
“So Doc, look at this engine. I opened its heart, took the valves
out, repaired or replaced anything damaged, and then put everything
back in, and when I finished, it worked just like new. So how is it
that I make $40,000 a year and you make $1.7M when you and I are
doing basically the same work?”
The cardiologist paused, leaned over, and then whispered to the
mechanic…..
“Try doing it with the engine running.”