I think samrat is looking to put ads in his app rather than advertise the app, so there is no cost - although influads are definitely not "cheap" for advertisers...
In any case, I would recommend influads as well. They are currently working with quite a few people with the same situation as you - people that have an app with moderate success and are looking to incorporate some non-intrusive, good-looking, and relevant advertisements.
In any case, I would recommend influads as well. They are currently working with quite a few people with the same situation as you - people that have an app with moderate success and are looking to incorporate some non-intrusive, good-looking, and relevant advertisements.