Up until last year, it seemed to be an unwritten (or maybe written) policy that the Windows client team wouldn't pay developers to write apps for Windows 8.
But that edict seems to have been rescinded. Microsoft is now offering developers $100 for each Windows 8 and/or Windows Phone 8 app they write, up to a total of 10 apps per Store. This limited-time promotion -- which started March 8 and runs until June 30, 2013 -- is known as the "Keep the Cash" offer. (Participants must live within the 50 United States and be at least 18, according to the fine print.)
Microsoft has paid for the development of Windows Phone, but not Windows 8, apps in the past. As The Verge's Tom Warren noted, not everyone thinks paying for app development is a sound idea. But Microsoft definitely needs more Windows Store/Metro-Style apps, especially given the fact that these kinds of apps are almost the only ones which will are able to run on Windows RT and Surface RT devices.
I've spoken with some business app developers writing apps for Windows 8 who've said Microsoft didn't pay directly for them to write for the platform, but did still indirectly fund app-development work.
Officials with Microsoft partner Sogeti, for example, talked about Microsoft funding "proof of concept" apps by playing matchmaker between devs and customers, offering devs some money up front for their app-development time.
Update: As a few readers have noted, $100 is not a whole lot of money when it comes to building true value-add apps. But as Microsoft is dinged repeatedly for the quantity of apps it has in the Windows Store and Windows Phone Store, it seems like the company is trying to play the quantity game, more than the quality one, with this particular promotion.