"Two years ago the Play store yielded 1/10th the revenue of the App Store, by common metrics. One year ago it was 1/4. The most recent stat is 1/2 -- still months old. Do you see where this is going?"

Yes, the Play Store revenue may be gaining on iTunes revenue. -- but per-app revenue in The Play Store has not necessarily grown. Revenue growth indicates nothing without the number of apps on each platform. Since the Play Store has more apps than iTunes, we cannot reliably correlate an increasing revenue (and a decreasing revenue differential) with increasing per-app revenue.

In fact, per-developer revenue represents more useful data than per-app revenue. Since the developer (firm or individual) pays the cost of residing on the platform, he also recoups the revenue. He can decide to reinvest revenue in more apps. Therefore we should not exclude developers with multiple apps from our model. So we use per-developer revenue instead of per-app revenue.

What is the per-developer revenue of The Play Store and iTunes?