I own a couple of them and quite like them, nice to use with a red dot to get some extra range when needed, and just flip out of the way when not. You will find them mainly used on the "tactical" style rifles in Aus like the Warwick, 7615's, etc.... as well as the people lucky enough to have access to semi autos.
I own the eotech one, which was close to $1000, as well as the vortex micro one which was about $450.
The aimpoint 3x magnifier itself is worth around $1000aud mark new, but it's also somewhat hard to find here so that could be a bit more, the larue mount itself is worth a couple of hundred and also hard to find here.
Just for comparision since not many places in Australia stock it:
https://www.scopedout.com.au/aimpoint-3x-magnifier - $1,134.98 without the mount (the prices for it with the mount on this website seem overly high and wrong)
https://www.optics-trade.eu/au/aimpoint ... m_store=us - (Eu store but they ship to Aus - 1500 aud with a mount, different mount though)