Cost per Click

Cost per click (CPC) is the average amount paid for each click on an ad, the shallowest measure of the price of getting a user to the site.

CPC is the cheapest and shallowest ad-cost metric, because it only tells the price of getting a user to the site, not whether that user did anything. That shallowness is its main trap: a low CPC is tempting, but if those clicks do not convert, cheapness is useless; a channel with a high CPC but a good conversion rate can beat a cheap one. So CPC should never be a decision basis on its own and must be followed through to CPA and then to customer acquisition cost. The point that matters for an analytics tool is that CPC lives almost entirely in the ad panel: both the click count and the spend are there. What the site tool does is show what those clicks did after arriving, so the quality behind the CPC becomes clear.