This thread has had an extra 100+ posts on it since I last looked at it. Has there been a for sale thread with anything like this sort of attention? I've seen it linked to from the UK pinball forum too, so it's getting linked to from other places.
In that respect, as far as the OP is concerned, it is an unmitigated success. People are talking about it, people who are in that end of the market would be speaking to him to find out what he really wants for it. If he had listed it for ~$12k or whatever most people would think a prototype would be worth it would've been lost amongst all of the other for sale posts.