1. A method comprising: receiving, for each of a plurality of mobile applications, application data associated with a respective mobile application of the plurality of mobile applications, the application data including different user interaction data associated with the respective mobile application; clustering applications of the plurality of mobile applications according to a classification; logging user interactions with each application of a cluster of applications for a plurality of users; generating an initial score for a first application in the cluster according to the logged interactions; and calculating pricing for content items served to the first application based on the initial score and an average score for applications in the cluster.