Google's ad extensions are now added to the Ad Rank, which already includes Max CPC and QS.
Our system for ordering ads on search results pages uses a calculation called Ad Rank. Previously, Ad Rank was calculated using your max CPC bid and your Quality Score. With this update, Ad Rank will also take into account a third component: the expected impact from your ad extensions and formats. In addition, we've increased the importance of Ad Rank in determining whether your ad is eligible to be displayed with extensions and formats.AdWords Now Showing More Relevant Ad Extensions and Formats [adwords.blogspot.com]