In 2011, Android Market (Google play) cost $25 for a lifetime developer account. You could develop apps on Windows, Mac or Linux. It came with an emulator. So for the cost of $25, anyone on any major developer platform could write an app.
In 2011, you could only program Windows Phone app on Windows (I don't even have a Windows machine where I live). Windows Phone Marketplace charged $99 a year for a developer account. You can say Apple did this to, or that it should be nothing, but apparently it was not a winning strategy. I know a college student who shelled out the $25 back then and published an app on Google Play, now he works as an Android developer for a Fortune 500 company. Perhaps the idea paying four times that, and on a yearly basis no less, to Microsoft, was off-putting. People can straighten their tie and say any business going off on such a venture can afford $100 a year as a gatekeeper, but it didn't work out so well for Microsoft. Apple was already in the pole position so they could get away with it.
But you're right, after throwing up these barriers to developer entry at first, they started raining cash on developers to make apps, providing developer shops to code it and so on.