But that's the thing - with the present level of technology, you can have a device that is, essentially, pre-programmed CNC to make AR lowers (which is what Ghost Gunner is, for example) for under $300.
To make a fully functional firearm from there, you also need a complete upper - can be had for another $400 or so these days; and a complete lower part kit with buffer tube and stock - can be had for less than $100. For a total of $800, some assembly required (or you can pay another $50 and have pretty much any gunsmith put it together for you).
So basically, a person can take GG and produce an unregistered, untraceable, no-background-check-required AR with it for $800-900. For comparison, the Bushmaster AR that was used in Sandy Hook shooting costs ~$700.
