Actually that Raptar unit on top is crazy light. It looks like a brick, but sure doesn't feel like it.
Wilcox Raptar: 2.85 g (10.0 oz) with battery
Leica 1600B: 180 g / 7.8 oz with battery
My problem with Leica's at extreme distance is keeping them steady. Sure the monocular can reach 1600 yards, but at that distance, I really don't know what part of the red square I'm lazing with, and the target is nigh on invisible at 6x power.
This rifle mounted beast definitely isn't for everyone, but I can see a legitimate application for it. With the crosshair matched to the rangefinder laser, the rifle has a lot more magnification and is much steadier than me holding a monocular.