cheap backup server

What is cheap backup server?

cheap backup server is high paying keyword (HPK), the CPC estimation ever recorded is about $109.13 per click. This value is estimated by Google Adsense Publisher experts in 2015. This keyword is really important for you to get more money with Google Adsense. 
See: what is HPK?

 

source: http://grepwords.com/1000000-top-high-paying-cpc-adwords-adsense-keywords-2015/