2,000 bhp Viper seems really cool. But would you want to buy a car already prepped like that? Or, would you want to be part of the build? As an example, ultra custom Harley-Davidson's generally do not appreciate in value as HD owners want to be part of the "artistic process" to create the machine.
Horses for courses. Most builds are done to chase a dream and the journey is as big a part of that as the end result, often bigger. But $250k spent on a $55k car is still only a $55k car with a premium on it.
For some, it makes sense to rather than spend $300k on a car (to buy/build and be part of the journey) - would rather spend just $100k and go racing now, leaving the depreciation with the guy who built it. $150k is a push for a custom car, but someone may pay it. Pro Tour cars can fetch good money - but if they have not taken shortcuts - very few could break even on a decent build, and that's with free labour.
I am probably $250k in deep over the years in one of my cars that started life as a $13k cash buy, but it would only fetch around $60k to sell it... that's the price of a hobby. It was fun, but now I'm older so next time I'd rather buy something built close to what I want and spend a fraction of that. I can't retire in my cars lol