Sure, you may try to place the in-app ads. Clickky's monetization platform will help you to place ads relevant to your users (the programmatic approach identifies your user and his interests and shows him the appropriate ads). It works by eCPM. One of the publishers received traffic from 11 geo locations in various regions. eCPM rates peaked at $61.5 in Russia, followed by $30.28 in Switzerland, $14.13 in New Zealand, and $9.45 in France. Overall, eCPM haven’t fallen below $0.65. He had a mobile web-site, not an app, but it doesn't matter.
The eCPM you get depends on users. Let's suppose that the app advertiser has some profile of users who will most likely install his app, use it and make in-app purchases. He is ready to pay money to attract these certain users, showing them the ads. When these certain users use your app, the system (RTB-based) connect you (publisher) and app owner (advertiser). That's why the eCPM is very high. Imagine, how much you are ready to pay as an advertiser for the particular user who will bring you at least $200/mo via in-app purchases. Yes, that's why some publishers may earn up to $150
Agree with @aiaran
that you should use multiple networks as they give you different fill rates in different GEOs. Unfortunately there is no best-ever solution on the market. E.g., now Clickky's monetization platfrom is now very good on Tier 1 countries, and maybe some other platform will monetize your traffic from Australia or Russia much better. In a month the situation may change, so you have to combine different platform and monetize yur traffic to the fullest.