At the motel checkout desk, Harry handed the clerk $50.  "I am sorry, sir" 
the man said, "but this won't cover your bill".

"The hell it won't!"  Harry barked.  "The sign outside says rooms are 40
bucks".

"But that doesn't include the food" the clerk explained.  "Your total is
$75".

"But I didn't eat any food."

"It was there for you, if you didn't eat any that is your fault."

Harry  glared at the motel employee for a moment, "OK" he finally said, 
"then you owe me $100."

"What for?" the confused clerk asked.

"For screwing my wife."

"But I never touched her."

"That's your fault," Harry shrugged.  "She was there for you."