All iOS - iPhone, iPad, iPod touch, Apple TV &...
There are a few mishmash threads on this subject.
I say we make it scientific! We need lots of entries to make it worthwhile. Try to use at least 3 months worth of data usage to make your average. Calculate it. Then choose one option:
1. Less than 100 MB
2. 100 MB - 499 MB
3. 500 MB - 999...