IIRC, my 1986 4/4 cost a smidgeon under £8000 new, which equates to about £23k today.
Although my car is about as unoriginal as you can get, I reckon it's probably still worth something like that.
Iso if you want to be sure of not losing any money from the purchase of a Morgan, simply hang on to it for a few years. They'll probably drop a bit up to around 5 years old, but after that they'll more than compensate for the effects of inflation.