Is $5b for Developers a Lot?

Google just mentioned that they paid out $5 Billion to developers since last I/O. Evidently somebody is buying paid apps. On average, that's $5 per 'active' user. I can't really tell if that's a lot or a little. By contrast, the last time Apple explicitly mentioned this number was when they had paid out $1 Billion, if memory serves that was at the iphone 4 launch and was the cumulative total since the first iphone. Their market has obviously grown since then.

I still feel like there aren't enough paid apps on Android, and evidently there is a market for them. Does anyone have other numbers and perspective on whether this is a significant amount, or just a large number in absolute terms?