yeah, i didn't see anything special about it either that would justify a higher than average price, especially a used model...i'm hoping someone that ownes/owned one will chime in
Look a little closer. It has a free float modular quad rail with rubber covers, Moulded rubber pistol grip instead of the hard plastic M-16 style, folding front and rear iron sights that are mounted on the flat top reciever and modular gas block rail, a CAR or skeleton style stocks, and the barrel is not the M4 style but a fluted barrel. There are a bunch of parts to interchange or add to this guns platform in the Bushmaster Modular Accessories section of the website. I personally think the price is a bit high as well but there are differences. Hope this helps!!