CPM = Cost Per Thousand. Cost per thousand (CPM) is also known as cost per mille. This is a marketing term used to show the price of 1,000 advertisement impressions. It is used by both online and offline marketers. If a digital signage advertisement costs $1,000 and has 100,000 ad impressions, that means an advertiser has paid $10.00 for every 1,000 impressions of its ad. The “M” in CPM is for the word “mille,” which means “thousands” in Latin.