Part of the ghostgunner appeal is indeed its appliance like nature, but it's an expensive appliance, and a limited one at that. Though it's small, doesn't require 3 phase, and doesn't require understanding how to program Gcode, the machine is still a CNC mill, and will require the operator to understand the tooling and processes involved as manual tool changes and moving of the part for different axis of cuts are still required. Even after the larger parts are made on the machine, the user is still going to need a 3rd party parts kit to assemble a functional firearm, so the only end benefit the ghostgunner has over a 3D printed part is that the frame/receiver is made from billet and you can mill your own slide.
Outside someone who really wants to be able to claim they made their own metal receiver, I really don't know who the target customer is. From what I can tell by looking at the spec sheets, it offers Ford Pinto performance at Porsche pricing. Considering the likely country of origin of the components inside one of these suckers (Assembled in USA), and apart from its convenient package, I really don't see the advantage to buying one of these over ordering a benchtop CNC off of AliExpress. At least with a mill that comes straight from the source, you'll understand the machine better during assembly, learn something about how CNC works, and wind up with a user serviceable piece of equipment that can produce more than just the handful of components the ghostgunner has been tailored around.