Efficient shopping

On the way to the airport, a boy came running to the car window with books he wants to sell. We negotiated for one and then for 2. We gave him our price and he wiggles his head so we thought we reached a deal. We took money out of our pockets just as the red light is about to change and gave it to the boy. He then kept close to the taxi screeming and arms in the air so maybe that our price was not his!