This is going to be an interesting conversation. (Sorry Mom if you're reading this).
How the hell do I explain what this message means to someone that's not a geek and couldn't care less about understanding geeky stuff. She just wants her iPhone to work.
We'll iCloud storage plans don't "just work".
And replying to my Mom with a "just subscribe to the US0.99 plan per month" is a stupid idea. First of all, she'll ask why. And rightly so. Which will only open a can of worms if I try to explain what it's doing in the background. She just doesn't care and nor she should. Second, she'll probably be pissed off that she has to pay a monthly fee for something that makes no sense to her and she sees absolutely no need for.
Now, I do see the value and pay for a 50gb plan right now. And I know that once I start to really use Photos I'll upgrade to the 200gb. But I'm a geek and she isn't. She's only using iCloud storage to back up her iPhone even though she doesn't know it.
As it is, iCloud storage is only causing my mom angst. And I'm pretty sure that's the opposite of what Apple wants to cause its users.
A good solution is if I could share my plan with her and take care of it all. I'd be happy to pay for a 1tb plan if I could share it with my family and make these emails go away.