Hey Michael,
I'd say they're worth about $275-$375. The version would affect that a little, as there were 3 over the years. A big negative about the MC 400F rearsets is the mounting brackets (plates). They are horrendously crude and appear to have been made in someones garage using aluminum plate stock, a drill, and jigsaw. That said, they do fit the Daytona which most other available brands do not (the exception being the 202 Racing kit).
As I recall, Doug was selling the last of his v3 400F rearsets in early 2012 for about $325 on a Spring Sale 'closeout'. When the shop closed they were selling for about $359.
(Full disclosure: I have 1 set of Moto Carrera v3 400F currently mounted on my Daytona. at least 2 sets of early version RD400C-E rearsets, and a set for the RD250/350.)