Actual cost-per-click (actual CPC) is the final amount charged for a click. Generally, you will be charged less (sometimes much less) than your maximum cost-per-click (max CPC) bid.

Actual CPC is generally less than maximum CPC. This is because in the Google Ads auction you will only pay the minimum amount payable to exceed the Ad Rank thresholds and pass the Ad Rank of your opponent (if any) below you.

Ad Rank has a big impact on actual cost-per-click (CPC).
CPC is calculated using the formula:
CPC = Ad Rank of Advertisers / Quality Score + $ 0.01
Pricing varies according to the advertiser’s ad ranking after you.