$8000 or so is about right for that guitar. As far as it being a "knockoff" of D'Angelico, remember there were very few master builders at that time ( D'A, Epi, Gibson and maybe Larson Bros) making big electric archtops. They all worked off of similar jigs and forms.
Behold the Gibson Switchmaster
Not button crazy, although it has enough knobs to keep you busy, busy, busy.
Plus that bizarro vertical selector switch in the front lower bout.