Google released a new Ad Rank formula last year, signaling a fundamental change to how it is calculated. Ad Rank is the algorithm Google uses in AdWords to determine how high your ad will rank and how much you will have to pay per click. Previously, it was calculated using quality score and maximum bid / cost-per-click.
Now, it takes into consideration ad extensions and formats. This means that your ad extensions and formats will play in role in your ad position and the price you pay-per-click.