Notice how this is the exact same psychology when it comes to managing money as a married couple: You'll spend anything to make your family happy, but it's also important to be responsible and make sure that there's always food on the table. (cheerfulegg.com)
An unwhitty customer or one that has low critical thinking skills get easily taken when the sales person drops the price down a few notches... same psychology. (religion.blogs.cnn.com)