Depends on what you want to develop; if you need the Windows driver kit then yes, those subscriptions are expensive (but likely worth it).
If you want the equivalent of app development on Windows (meaning little to no access to kernel sources and such, just a native UI), you can use the free version of Visual Studio without the MSDN license [1]. The license allows commercial development even with the free community version.
You still need to pay +/- $20 to MS to publish apps to the MS Store, but because Windows isn't a walled garden and barely any Windows users are using the store anyway, you probably don't need to bother. If you do pay, it's not a subscription either; the costs are only made during registration. Just like with Google, this keeps down (but does not prevent) the creation of spam accounts.
For most app developers, the infrastructure you get in return isn't worth the $100 / year, because most apps don't get that many downloads at all. Hosting APK or IPA files can be done for one or two dollars per month for the first few hundred or even thousand users, and by extending the store ecosystem, you're also adding value to the platform itself.
For iOS you can argue that the manual testing of the application needs to be paid somehow, but the manual testing Apple performs don't benefit you as a developer in any way; they serve benefit the end user that downloads your apps, so those costs should be recouped from the user (as part of the iPhone sales price and the mandatory 15-30% cut Apple and Google will take).
If there was a way to build and publish applications without the subscriptions, the fee might be reasonable if Apple can defend the $99 / year. With the walled garden they've set up, there's no competitors, and therefore there will never be an alternative developer toolkit like those you can see for the Android ecosystem.
[1]: https://developer.microsoft.com/en-us/windows/downloads/