I think you are right. People I know who have real money are increasing their holdings of "real" things of value, like property, and various "objects" like art and, yes, cars. Let's say the bubble stops going up, can you really see our cars losing half their present value in a few years? Mercedes is more of a blue chip kind of brand with generally slow but consistent appreciation over time. There may be sharp drops, but I very much doubt it will be significant over time.
And a classic car is more fun to own than a stock portfolio. Non-car people ask to see my car at house parties, they smile and admire the old car as I give the tour and have a smile plastered the whole time when I give little rides. I am sure you have had similar experiences. You cannot do that with stocks!
Jerome