Also note the near total absence of pro gear - no Nikon D3/D4 entries, for instance, still I would expect those cameras _on average_ sees a lot more use than yo

Also note the near total absence of pro gear - no Nikon D3/D4 entries, for instance, still I would expect those cameras _on average_ sees a lot more use than your average D3100, for instance. (Also, chances are they'd skew the lens numbers significantly - while kit lenses come and go, pro glass tend to live much longer before being upgraded. (The 24-70mm f/2.8 which you often see around single-digit Nikon bodies, for instance, was the standard zoom for 8-9 years before being given an upgrade last year)