CPC depends upon the blog’s Niche or Topic.
Health, Finance and Insurance are mainly with high CPC while Jokes, Movies, and Facts are mainly with low CPC. Technology and Computers are Medium CPC.
The origin of the traffic of your blog is also the reason for the lower or higher CPCs. If most of your blog comes from a Developed country such as USA,UK,Canada then its CPC will be higher, but if your traffic comes from countries like India,Pakistan or Nepal then your blog’s CPC will be lower.
Because Purchasing Power of developed countries is more than those of developing countries. There are some factors that affect your CPC, such as the location of ads, Ad Blending, and the type of ads (Text, Image, Videos) etc. They can also be optimized by some methods.