Does Buying Extra iCloud storage include all devices in my account?

I am getting email messages about my iCloud storage being at 75% capacity. I have multiple devices in my name, 2 phones, an iPad and a computer. Would buying the extra storage be something I would only need to do as a single purchase? Would all the devices then benefit? The message about my storage capacity isn't specific and I suspect that my assumptions about covering all devices is true, but I would like some confirmation. I actually had purchased extra storage but the CC I used expired and apparently I wasn't notified. I suspect that is the reason for the warning.