"(1) Never give anything away for nothing. (2) Never give more than you have to give (always catch the buyer hungry and always make him wait). (3) Always take everything back if you possibly can."

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I suppose that one of the psychological principles of advertising is to so hammer the name of your product into the mind of the timid buyer that when he is confronted with a brusk demand for an order he can't think of anything else to say, whether he wants it or not.

— Robert Benchley