How much for all night?

The woman seated herself in the psychiatrists office. "What seems to be the problem?" the doctor asked. "Well, I, uh," she stammered. "I think I, uh, might be a nymphomaniac."

"I see," he said. "I can help you, but I must advise you that my fee is $80 an hour."

"That's not bad," she replied. "How much for all night?"