The cost to advertise on an app can vary widely depending on factors such as the size and engagement of the user base, the type of ad, and the targeted audience. Advertisers typically pay for app ads on a cost-per-click (CPC) or cost-per-impression (CPM) basis, with prices ranging from a few cents to several dollars per click or impression. The exact cost of advertising on an app will depend on the specific app and the campaign goals of the advertiser.