One reason for low CPCs is the topic. If you have a website about fowers, it seems unlikely to AdSense and advertsers that one would think about buying an iPad while visitng your posts about fower arrangements. Since fower arrangements are not that easy to purchase through the Internet, competton for this topic is rather low and, therefore, also the click prices. Another reason for low CPCs is the locaton of the trafc. Head over to your AdSense account and check out the Countries secton of your Performance Reports. If your content is in English, chances are you have the best CPC for visitors from the US, UK, Canada, and Australia, but rather low from India, South Africa, or Nigeria. The reason is mostly the lower income in these countries. If we are already in the Performance reports of your AdSense account, check out the platorms secton. I bet that you will be surprised about the huge diference between the CPC and RPM of mobile visitors compared to desktop visitors. Leverage this knowledge by increasing your mobile income with better ad placements and also try to atract visitors from well-paying devices.