Actually not too bad IF you start with a bare receiver. If you build it as a pistol FIRST, it can be switched back and forth between pistol and rifle configurations legally at will. But if it left the factory as a rifle, it must stay a rifle.

So, since this started life as a pistol, I can use it as a pistol for two weeks in firearms deer season, then as a rifle the rest of the year, by simply adding a 16"+ barrel and buttstock. That way, it's not an expensive two-week-a-year "toy".

AR-15 rifles and pistols cost about the same to build, so figure a grand or less for an average build. Add in another $600 for the suppressor pictured and $200 for the NFA tax stamp.