I've seen the video of this car running/driving (in very cold Detroit, MI weather for that matter) and it is sweet. I mean sweet. Ran like a beast and sounds bad to the bone. The original gold color is retro-cool in my opinion. Unlike all the red, blue, yellow repainted ones out there. That coupled with the fact that A) it's a Demon (not a Dart or Duster) B) does come w/ a complete 4-speed setup and C) $18,000 is the asking price in my opinion is listed pretty fairly to start talks...not to mention the extra hood, the suspension work it's got on it etc...
I got $13,500 in Oct 2009 for my nice '67 Dart GT 6cyl car w/ a 340...it was a notch below the condition and desirability of this Demon.
If I hadnt had some issues come up I'd be at Scot's door w/ an offer. For a turn-key street car that you can cruise to the track, click off a low 12 or high 11sec pass, then cruise all night on Woodward that is stone cold reliable, looks cool, is show quality and is something you dont see as often as the typical Dart/Duster, I'd say the asking price is a pretty fair starting point.
Just my humble opinion though...good luck with the sale Scot. See you at Autorama, I'll stop by and say hello and check out the Demon.