Lorne - in my view there is no magic to this.
In the past in the UK (main mog market I guess) there has been higher demand than supply.
Mogs don't get retired to a scrappy after 5 years like most Euroboxes do, so the numbers available in the UK are constantly rising.
similarly (I would guess) that the available group of potential purchasers keeps falling, a function of age, demographics, and viable alternative.
Perhaps the US will buck this trend - if theres enough enthusiasm for the marque and a low enough supply values will stay high for the moment.
I don't know whether this was supposed to be just a funny post, at least the remark on what happens in GB to Euroboxes after five years made me insecure.
There are/were two reasons Morgans were restored in UK:
1. Many cars are like family members.
2. Financially it made sense.
Look what happened with Jaguar E-types. When prices rocketed much money was invested in cars nobody had touched before because it didn't make sense to invest money.
