For "non-enterprise" developers, I would suggest Corona instead, restricting in-app purchases and adding a revenue limit for the free/cheaper tiers feels like the best model in my opinion. It doesn't compromise at all the experience for developers:
Except that you need to use Lua (and most Xamarin customers are C# shops) and you don't have any control on the build process of the app. I hate waiting for some cloud service to send me back a binary version of my app. A slightly better alternative for Lua coders is to use Corona Cards (you do the building on your own machine) but this doesn't have a free version.
I think a much larger issue is the current (and onwards) generations of indies, enthusiasts and kids who are actively prohibited from trying Xamarin.