MS, you pay one time for the OS. Android you technically don't need to pay at all if you go AOSP. Both still require hardware to support the OS, though.

>And no. Paying for the phone is not a viable way to pay for the OS. That incentives the phone maker to ditch OS updates for old phones.

They do that anyway. mobile support is much lower than desktop which tends to guarantee a decade or so. And it's not like IOS is licensing out to other OEMs anyway.