The overwhelming majority of apps on both platforms are free. Among what I could charitably call "pay-worthy" apps, my personal impression is that there are probably a magnitude more on the iOS platform. Indeed, this submission seems to talk to that, pointing out that there is more of an opening for quality apps on Android.
I've never respected any number of apps metric because they are overwhelmingly chaff.
I know there are a lot of arguments AGAINST the play store, but this is quite real and imo quite valid.