So, if it's that good, and he wants to sell it, the benchmark has been set by this car.
The value, as Rusty said, is set by the market place and this one knocked it out of the park because of its attention to detail and the finished result.
Here's a kicker for you.
If that Demon had rack and pinion steering, a 6.1 Hemi ,tubular suspension with an RMS or HDK suspension system, 4-link, coil overs, upgraded audio, it would have gotten even more money than what it sold for.
Restored is gradually being replaced by RestoMod as that's what most new buyers are most comfortable owning.