The numbers for android are appealing as a third party developer, but how much money is being spent in the android app store? Ads are viable, but hardly ideal for all types of apps.
I've seen a few things suggesting lower sales rates on Android, but since almost none of them adjusted for installed base, I'd be wary of drawing any strong conclusions. But even if they are correct in their inferences, they were still suggesting simply lower sales (e.g. a third or half iOS) not that no-one was buying apps at all. It's hardly a black and white picture, particularly with the introduction of iAds by Apple.