No, Windows still has Windows tax, which is why I always choose "No OS" when buying a machine. MacOS/iOS/iPadOS were never for sale separately, so we can't judge the price. Android sure is subsidized though.
Android does have a cost. While the OS itself is free, any manufacturer that wants to put Play Store, which is almost every company outside China, needs to pay Google a license fee, which effectively pays for Android. Of course there are also ads everywhere in Android and Android apps that helps pay the bill.
> MacOS/iOS/iPadOS were never for sale separately
Mac OS was though. OS X 10.0/10.1 were sold for $129 as an upgrade for Mac OS 9 users. Apple continued to offer OS X as a paid software product up to 10.5 or 10.6 (though it was also bundled with new Mac purchases).
[https://en.wikipedia.org/wiki/MacOS_version_history]