I've been hanging to play a NGG. For a game made late 1997 and a LAWLOR design they are very scarce in AUS.
The US collectors seem to hang onto theirs which I guess is a good sign.
The best bit is no licensing on them and Wayne has plastics and other parts very cheap..
Regarding price - no idea given I have NEVER seen one for sale locally in the time I've been collecting.
I would guess somewhere between the $4000 to $6000 mark, but I would be completely guessing.