Did that car have numbers:
Motor?
Original Fender Tag? No issues/doubts?
Buildsheet?
How many panels needed replacing for the resto?
Fact of the matter, it's a 440 4bbl automatic car. A comparable docs pre resto condition 70 Challenger 440 4bbl auto is $50-$60K car. With a lot bigger buying audience.
Also I think timing is an issue. M-code A-bodies are a niche market, more savvy than average. A smaller group of buyers. That cars' pre resto condition was fresh in the mind of a lot of potential buyers.
Sometimes a little time allows the current condition to stand on its own. This red M-code might change few hands, a couple years will go by, it's history will be forgotten some, and bs embellishments added by used car sellers. It'll be advertised for $69-75K and actually sold for $58K-$60K