So I was reading the Sony FY2018 results thread on resetera, and found a posting by ArmGunar.
Apparently he found a slide that showed offical sell-in numbers for the PS3.
So there we go, offical numbers for PS3 at 87.4m units.
Necro-bump this 2020: http://gamrconnect.vgchartz.com/thread.php?id=229249
Bumb in 2021: http://gamrconnect.vgchartz.com/post.php?id=9047071