It says that the prices of 50yr old aircraft have reverted back to their true market clearing price reflecting an unrestricted supply of aircraft. When virtually nobody was making new aircraft for over a decade, supply increased by zero, and in fact decreased with every smoking crater. Demand was fairly stable. Hence, increasing prices
Now we are in a situation where supply is increasing (they're making new planes, and plenty of them) and demand is decreasing (you, I am sure, have seen the numbers of active pilots). Move the supply curve down, and the demand curve down, and your market-clearing price is going down.
This is not surprising in the least. Is the 1961 210 a capable aircraft? Sure. How many people in the market need those capabilities? How many give a rats patootie if it has the latest/greatest ADF/LORAN/KX170B avionics? Clearly, not enough.