CPC is based on user (location, interest, previous visited websites etc), along with site content (e.g loan advertisers wants to be
seen on relevant sites, and not dog sites)
CTR is based on ad placement (click-through-rate of ad) along with ad relevance to user.
Make sure the traffic you're sending are being sent to a relevant site for the majority of them. Optimize placement of ads. Provide good
content (as in language, text ratio and # of ads on the landing page) and you should see income going up.