"The fallacy of old car appreciation"
There is no inherent fallacy here but the statement has a lot of ambiguity.
"Old car" is about as ambiguous as it can get. It would be nearly impossible to lose money on one of the 6 remaining Shelby Cobra Daytonas or a Gullwing Mercedes, or name your own favorite iconic car of high value and limited numbers. Here on a Mustang forum however, where "old car" implies cars like we all have, mostly run-of-the-mill FORD Mustangs, one of the most produced cars of all time, the brutal truth is that almost exclusively, none of us have a car that falls into the same category as these other "old cars".
Again, there is no particular fallacy of old car appreciation. It is true that SOME old cars will always appreciate, but a 1966 Convertible, etc, are just not in that same category.
I always think about it this way also; There's the same amount of work, more or less, in replacing rusty sheetmetal on a Pinto as there is replacing rusty sheetmetal on a 1957 Ferrari Pontoon Testarossa. So even the maintenance argument falls down at a certain point.
So the bottom line is, your starting point determines what you end with. I've made the same mistake. I dumped TONS of money into an old british car with a very low final value for even a pristine car. I lost my behind on that deal and I realized that, if you want to make money, you're best off starting with the vehicle of the highest end value that you can afford.
Just like with anything, if you want to make a million dollars, you're best off starting with 2 million dollars.