Our marketing, retail, and finance teams set three criteria that any new marketing initiative would have to meet to go forward: It had to be affordable (an eye-catching but financially unsustainable approach was out of the question). It had to drive the right customer behavior (that is, nudge customers to buy more from Amazon). It had to be a better use of funds than the obvious alternative, which was to invest those same funds into actions that would improve the customer experience, such as lowering prices even further or improving our in-stock rate.