With so much consumer activity moving online, retailers must be strategic in the ways in which they market products to internet shoppers. A significant part of those strategies will center on comparison shopping engines (CSEs) such as Google Shopping, PriceGrabber, Shopzilla and others. However, marketers are still struggling to make informed, profitable decisions about which CSEs are worthy of their budgets. Too many retailers look first at the cost per click (CPC) and never dig deeper to determine actual CSE value. In reality, it's the revenue-per-click (RPC) data that should influence retailers’ CSE investment decisions. Marketers that know how much revenue each click generates can then determine the return on investment by considering the CPC.