I'm not surprised that there are no replies to this question. I've been researching hybrid mobile app monetization with limited success. I'm personally more concerned with incorporating mobile ad networks (AdMob) and socialization networks (Socialize, Facebook, Twitter) in hybrid mobile apps based on HTML5, CSS3 and JavaScript. I'm focusing on Android to start. PhoneGap has an AdMob plugin that works. Eclipse also has a PhoneGap plugin by MDS that makes it easy to get started.
As you get further away from native Android and closer to the cross platform build environments it becomes more difficult or impossible to use various required SDKs for monetization and socialization unless there is an existing plugin or you (and other developers) are willing to write a plugin.
Most of the cross platform build systems (PhoneGap Build, Icenium, Monaca, Titanium ...) and the MEAPs (OpenMEAP, Convertigo, WorkLight, Feed Henry, Antenna, Appcelerator...) currently have no support. Apparently, monetization and socialization are low priorities in the race of the cross development platforms.
With respect to your question about in-app purchases for cross platform mobile development, there are two exceptions that I am aware of, the Intel XDK and the AppMobi Cloud Services SDK. The Intel XDK, largely based on it's acquisition of AppMobi and it's HTML5M App Center, has implemented this through 1Touch.
http://html5dev-software.intel.com/
http://www.appmobi.com/
http://www.appmobi.com/amdocs/lib/Article-1TouchInventory.pdf?r=4960
They also have references that advertising will be coming soon as well.
You can also develop hybrid Intel HTML5 apps without using the Intel XDK by using the AppHub Cloud Services.
http://www.html5dev-software.intel.com/amdocs/lib/Article-DevelopingOutsideXDK.pdf
Good luck.