To select content for presentation to a viewing user, an online system maintains multiple bid amounts associated with various content items. Content items are each associated with multiple bid amounts, with each bid amount specifying an amount of compensation to the online system and identifying a user, so the bid amount identifies an amount of compensation to the online system for selecting the content item in place of content items associated with the identified user. Based on users identified by bid amounts in various content items, the online system generates connections between content items and determines a group of content items including content items connected to each other content item in the group. Using connections between content items in the group, the online system selects a content item and determines a price charged to a user associated with the selected content item.