All respondents to this thread make excellent points. Missing here I think is a remarkable aspect about these classic cars. We can work on them! This forum, and other like it,was born of “tinkerers”. You can get your hands dirty, curse up a storm and commiserate with fellow tinkerers. The cars may go up and down in price, but it is the joy of ownership that imbues the value. Whether future generations share this spirit is doubtful. Open the hood of any car made in the last 30 years, and then just shut it. If you are looking to make money, there are many more established methods.
Fair call but think there's a distinction for 'investment' cars vs what are just cool old cars. I'd suggest a well done CSL is an investment car, as is early Alpina stuff or say cars with a racing history. Your average CS will continue to climb in value assuming demand remains for both the CS and on assumption that CSL values continue to rise. Put another way, people that love the CSL but can't find (or afford one) will grab a CS. Think can get a good idea on how E9s will travel in the long term when you look at the 911. People love the 911 because of the design and then based on budget they decide what type of 911 they can afford. My gut says as a general trend that non collector grade cars will plateau and then fall away as demand changes. Try and sell a Model T these days. Other cars that have a cult following will continue to hold up or increase - the e30 is a good example.