I've watched two specialist cars (not Morgans), that were known to me, go through exactly that pattern. In both cases they started off at £40k plus and were eventually sold at auction below £30k.
I've also watched dealers run a classified ad, as well as an auction, consecutively on Car & Classic; which ends in them selling the car for far less than the price advertised in the classifieds. The most recent example I can think of being a car listed for £69,500 via a classified, only for the dealer to sell it for £47,500 via auction. Considering the buyer pay the end auction price on C&C, this was the end price they paid - no auction or hidden fees. I've watched this happen time and time again over the past 4-6 months. In my humble opinion, the tide has turned and the market where car prices, across the board, were inflated due to lack of supply during Covid, even impacting VERY strong residual values on used cars, is no longer there. The same has happened in the property market; the people trying for inflated prices are sitting with their properties unsold and most agents are struggling to educate them that the market has softened greatly.
The issue with things like C&C auctions, Collecting Cars, Bonhams, etc is that they show the public, in real time, what cars are being sold for; furthermore, when potential buyers see cars selling for nearly 32% less than they are being advertised, that further impacts confidence in the market place. As for cars sitting unsold for 12-months+, that only hammers the point home.
Another example, the car that was mentioned in this thread: there are two Aero S1 GTNs for sale - both at nearly £100k - the best bid one has had was £70k and the second time it went up for auction 4-6 weeks later, it only made circa £55k (that was the most recent auction and iirc about 1-month ago). Also, to confuse things further (and not aimed at Morgans for sale) but I have seen more than a few auctions 'won' only for cars to reappear on the same dealers site back for sale 'due to an non-paying buyer' - really? A non-paying buyer or the stooge driving the price up on the auction ended up over cooking the interest and winning the auction?
As for the Aero, it was, and will always be a niche product. MMC, in later years (post Aeromax), made the situation confusing by adding various niche runs, either proclaimed to be limited runs, or ended up being (the coupe) due to changes in focus, parts, perception of what the customer wanted and so on. This, in my opinion, muddied the waters further and made valuing these cars more challenging. I could write a book on Aero product values and fill it with both fact, stories, examples and opinion but in all honesty, I think it boils down to too many variations of a similar niche product and confusion in the market place.
Add to the above that, unless cared for diligently, the Aero can suffer from age related issues (corrosion, electrical / electronic niggles, etc) and many look shabby, in spite of owners wanting inflated prices. Mine was as cherished as they came and in later years it was even more cosseted and never driven in the wet and yet it still suffered from issues.
So, you have an inflated market, of a niche product that most buyers don't truly understand and that, in my opinion, is not ideal. The S1 seems to have found a price point, albeit the ones advertised have remained unsold for awhile; however, I think they have found a value where people who want one can buy in knowing their money is relatively safe and they aren't over paying. I don't think the same could be said for the rest of the Aero Range. Who decides that an Aeromax is worth X when there are 100 more of them than the Coupe, which is Y? Who decides that an SS is worth Z, an S4 W and an S5 V? Ultimately, I would suggest the market and if cars aren't selling, then there is a reason why.
They are great cars - and if you know them well, there is no doubt in your mind how nice they are to drive - but the issue as I see it is most potential buyers won't know this, they will be 'new' owners, and therefore, in a confusing market place, they will take the safe option and buy a known quantity from a mainstream brand because it is easier to gauge value and risk (retained value over time).