With thanks to our friend Bruce Kesler:A guy goes to the Dr. for a chest cold. The Dr. listens through his stethescope and prescribes something. The bill: $100. The guy says: $100 for five minutes!?! The Dr. replies: No - for twenty years of education and experience to know what's wrong in five minutes.
Or, the plumber visits the Dr.'s house for a repair, and hands over a $100 bill for a 10-minute fix. The Dr. says: I only make that for 1/2 hour. The plumber replies: That's why I stopped being a Doctor.