Here's some interesting stats compiled from 2,600 AdWords accounts that ran Wordstream's AdWords Grader in Q3 2012. [wordstream.com...]
My analysis shows that, in the last quarter, the average costs per click (CPCs) have declined significantly in the last quarter (-16.5% for Google Search, -18.2% for Google Display Network), while click-through rates (CTR) were mixed (-12.4% for Google Search, +13.8% for Google Display Network).
Offsetting those declines are an impressive growth of ad impressions and clicks (clicks were up +21.6% for Google Search, +29.1% for Google Display Network), which more than made up for lost revenues.
My take is that the trends we’re seeing in the Google economy create a win-win for both AdWords advertisers and Google.
A larger available inventory of impressions, combined with lower CPC, means that PPC advertisers are now literally able to get more customers for less money.
It also opens up Search Engine Marketing to more advertisers, including perhaps advertisers for whom the economics of search might not have previously worked out at higher average costs per click. (Just as SEO is harder for small businesses with lower budgets, so is PPC.)
From the infographic: Average CPC Google Search $0.53 down 16.5% from Q2 Google Display Network $0.35 down 18.2% from Q2 Average CTR Google Search 3.47% down 12.4% Google Display Network 0.18% up 13.8%