These stats are probably put together by computer, on the basis of Morgan = sales volume too low- therefore use average.

As others have said the real world does not bear this out and perhaps just as well, the Morgan secret might get out.

Real world example. Morgan 44 sport purchased Jan 09 for 26K
sold to dealer 6 months later 26K. Not sure on the percentage loss but it wasn't anywhere near 50%.
Same car sold for 27.5k and is probably worth something similar today. The 44 Sport was at the lowest price end of Morgan products and is perhaps the end least likely to see significant depreciation in the early years. Roadsters and Aeros will have a genuine loss but the curve of appreciation as new car costs rise bring some values up again, probably due to the scarcity of these cars.