Btw $200 is not throwaway money for everybody.
You don't, you can perfectly develop an android app without owning an iphone
BUT, if you're using features from another ecosystem, let's say something like an authentication system that has requirements, you have to fulfill those requirements, otherwise skip the feature.
Same goes if you want to support hardware-level U2F, you're gonna have to buy a key then.
I don't know how that's news for anyone, Apple has been doing this forever and they explicitly chase that goal as far as I know.
If you're saying "yeah, I want to support iOS/Sign in with Apple/AirDrop/Screenshare/Any other Apple feature" then you're entering the need of having more things to do with Apple. That's the cost of joining and leaving the ecosystem they created for themselves.
End users say, "I would like to be able to sign in with xxx." Developers say, "Your OS vendor doesn't want you to."
If I want to add "sign in with apple", I need to read some docs, then read a bunch of forum posts because the docs are incomplete, then go out and buy a used iphone somewhere, and you think that is completely normal??
I don't see any reason to defend that, it seems to be only in Apple's best interest, not mine.
Anyway, it's not $200 for a test phone, it's $200 just for a 2fa device. Meanwhile Yubikeys are $20 and have better battery life.
Personally not a fan of either, separate email/passwords everywhere is what I prefer. But I cant say I have come across a non-apple service/site that offered apple login.