I'm not certain why folks are talking about cars they've restored to working order, the kind that get taken out on weekends when the weather is just so, as if that's the same class of vehicles the article is discussing. I used to know someone who owned a bunch like the article describes. To him it was an investment. Some had undergone expensive restorations like the article describes, they were meticulously stored, people were paid to maintain these not-driven vehicles, etc. Well, this guy wasn't young, but he died kind of unexpectedly. In a few weeks he went from not feeling well to gone.
So the family sold the cars in one auction at one of the big events like the Concours d’Elegance. This was not a sale timed to maximize the return but rather a sale to free the family from the obligations of ownership. Even so, it was 30 or so vehicles and they went for about $70 million.
The cars in this article are more like artwork investments. These may get three miles added to the odometer in the course of a year with multiple event showings or loans to museums. The cars are absolutely drivable but they are not driven.