I have developed several small apps for Windows Phone. Most of the time it is just to test how publishing an app works. I have developed an app for wp7, wp8.0, wp8.1 and universal apps and they are all free in the windows (phone) store. I try to earn back my developer fee of 19 euro by adding some small ads to it. I have used the adrotator version 1 and version 2 plugin and Microsoft's own admediator.
You can download that visual studio extension of the visualstudio gallery website.
and you can read how to use admediator on msdn.
my three ad networks are:
My conclusion: pubcenter has the best revenue and smaato serves the most ads. Please let me know if you disagree or have some advice. You can download my excel report here.
p.s. here is a 27 minute video of the admediator control on channel 9.
p.p.s. more info on the windows blog http://blogs.windows.com/buildingapps/2014/11/07/how-to-maximize-the-impact-of-windows-ad-mediation-for-windows-phone/