Higher CPMs usually occur when advertisers target premium, high-intent segments because those users convert more and are worth more per impression. Ad placement matters: viewable, above-the-fold placements on reputable sites command better rates than below-the-fold or hidden slots. Ad format and creative quality influence CPM too; rich media and native ads drive engagement and higher bids. Supply and demand dynamics play a role. Brand safety and viewability standards attract premium buyers, widening the gap. Ultimately, differences reflect perceived conversion potential, placement quality, and buyer competition across inventory.