Margie received a bill from the hospital for her recent surgery, and was astonished to see a $900 fee for the anesthesiologist.  She called his office to demand an explanation.  

"Is this some kind of mistake?" Margie asked when she got the doctor on the phone.  

"No, not at all," the doctor said calmly.  

"Well," said Margie, "that's awfully costly for knocking someone out."  

"Not at all," replied the doctor. "I knock you out for free. The $900 is for bringing you back around."