I reckon it would cost you that much if you ordered this with a new boat .
I was told that the two leccy battery box mounting points in my boat ( there is nothing to them - just bent 2mm aluminium plate welded to the floor ) cost $400 at the time of build.
Guess it depends also on the level of workmanship as well - is it just a weld or made to look like part of the boat ... using alloy extrusion as part of the build ?
Chris