The Case of the Clever Patient

Khusu was walking with his friend, Seshan, when he suddenly complained, “I have been experiencing frequent headaches for the last fortnight.”
Seshan suggested, “We are near the well-known physician Dr. Rao’s clinic. Why not consult him?”
Khusu inquired, “What is his fee?”
“He charges five rupees for examining and prescribing for a patient,” replied Seshan.
Khusu agreed to meet the physician. Seshan, who was familiar with Dr. Rao, introduced Khusu to him. While Dr. Rao examined Khusu and wrote out a prescription, Seshan remained silent.
After leaving the clinic, Seshan remarked, “You never told me that you were suffering from stomach trouble and heart palpitations as well!”
Khusu smiled and replied, “I only have a headache, but my son suffers from stomach trouble, and my wife has palpitations. Why shouldn’t I ask the physician to prescribe for all three of us for the price of just one consultation?”