I certainly respect the experience and knowledge of a former classic car appraiser. It is their job to determine a fair market value for a vehicle without bias.
Individual objectives also come in to play. It may be beneficial, in some cases, to sell the car in a timely fashion and move on to the next project rather than wait months or years trying to get top dollar for the car. Like it or not, classic car prices are in decline and have been for several years. A quick sale at a reasonable price may be the prudent option.
In your example of ask for X and anticipate Y, when Y doesn’t hit the table then one may need to consider that Y is still too high of a price. Otherwise , the inevitable outcome is having a collection of items that have perceived values which exceed reasonable market values.