From The Art of Thinking Clearly by Rolf Dobelli:
In his book Influence, Robert Cialdini tells the story of two brothers, Sid and Harry, who ran a clothing store in 1930s America.
Sid was in charge of sales and Harry led the tailoring department. Whenever Sid noticed that the customers who stood before the mirror really liked their suits, he became a little hard of hearing.
He would call to his brother: ‘Harry, how much for this suit?’
Harry would look up from his cutting table and shout back: ‘For that beautiful cotton suit, $42.’ (This was a completely inflated price at that time.)
Sid would pretend he hadn’t understood: ‘How much?’
Harry would yell again: ‘Forty-two dollars!’
Sid would then turn to his customer and report: ‘He says $22.’
At this point, the customer would have quickly put the money on the table and hastened from the store with the suit before poor Sid noticed his ‘mistake’.