Mad of Free Offers

Last sunday myself and my wife went to stores. We need to take tea. This time I want to taste different tea brand other than my routine one. After spending one hour in stores i have arrived to a conclusion of seleting two different brands of different flavoured. Now I requested my wife to help me in choosing one out of these two. My surprise she brought another brand and insisted me to go for that brand as that company is giving 6 tea cups as free offer with that tea. I really surprized how free samples, freebies etc., are influencing customers. How people are mad of these free offers?