I did survey of Android side of things during winter break right after Ice Cream Sandwich came out[0]. As I recall most of the severe fragmentation cases were low-end handsets which were typically behind a version or more already when released.
The point is presumably that there's no equivalent in the Apple ecosystem at all. If you want an iPhone for even close to the price of a low-end Android phone, your only option is a second-hand 3GS which is also one major version behind and no longer getting updates (or the equivalent at whatever time that survey was done). Except that, because Android can update many of the bundled apps seperately and iOS cannot, you're actually worse off.
[0]: http://www-users.cs.umn.edu/~okamoto/map.png