John’s dog isn’t doing too well, so he takes the dog to the vet.
The vet looks at the dog, shines a light in its eye, lifts its tail, and then turns to John. “My diagnosis is that your dog is dead.”
“What?” says John. "I don’t believe you – how can you tell that, after hardly doing any tests at all?
The vet shrugs and says, “Okay, I’ll do one more test.” He leaves the room and comes back a minute later with a mean-looking cat, twisting and yowling in his arms.
He holds the cat over the dog’s butt. The dog doesn’t move.
He holds the cat over the dog’s torso. The dog doesn’t move.
He holds the cat right in front of the dog’s nose, and the dog still doesn’t move.
“Okay, okay,” says John, “I believe you. How much do I owe you?”
“Five hundred and twenty five dollars,” the vet says.
“Five hundred and twenty five dollars?!” shouts John. “That’s ridiculous! Why would I pay you that much?”
“Well,” says the vet, “It’s twenty five dollars for the office visit, and five hundred for the cat scan.”