Lots of reasons, on these sites:
https://www.google.com/search?q=why+are+over%2Funder+shotguns+so+expensive%3F&btnG=Search&client=opera&oe=utf-8&channel=suggest&gws_rd=ssl
Still I do not get it..
I have Turkish one I paid $250 for, and it patterns great,but no support for gunsmithing.