Agree with Frank. Depends on the RGB board (outputting csync or composite video), how the install was done.
Same with the mod switch. Nice one from gametech or something else?
I've sold recapped pc engine duo with mickris RGB (sync on composite, not csync) and gametech region mod for around $250. Ac adapter and one controller included.
Seeing how you're throwing in an everdrive though, I think that, assuming it's good mod work, it's a very fair price