For me, with my continuing-search for a 156 V6, "well over the odds" is a matter of confidence in the seller first. Then the car.
The Veloces car which I missed had the provenance which made me feel, among the lower-priced cars, that I should take the risk @ >£2.5K.
So, I think I agree that values have been talked down. Enthusiasts say, on here, what they've done/ need to do, to get their cars into shape. A shape which non-enthusiasts avoid cos of cost. Low prices for 156s might be the result of potential-buyers budgeting for the worst condition?
Nah, its simpler than that. Alfas on the market now at the couple of grand region are in one of two states.
A) Well cared for and maintained, so no point selling as the cash input will be lost. Won't come up for sake often.
B) Dog rough and knackered, sold by people out of cash to maintain them, or who bought on a whim which backfired. Generally multiple recent owners, little recent service history, you wouldn't want one as they'd be a money pit.
What you really want is
C) Well maintained car that's being sold for a reason, upgrade, change of lifestyle, change of location. In good nick, but the owner needs to move it as a dealer won't touch it, and we buy any car is offensive.
As before though. Decent GTAs needing some minor spanner work start at £4k. And running and service costs are pretty much the same as 2.5 V6 models.