I agree with what you are saying. I doubt the one off cars will pull any more money then a non one off car once the market has enough supply. If a guy has a huge social media following and his car is whore'd all over there I don't want that car since it'll forever be "XXX's old car." Once you are in the type of price bracket that Bugatti, Pagani, etc. sell for you can spare the few extra dollars to get a new one and not have someone else's old toy. Plus it seems one of the major manufacturers has a new one off around the corner every year.
If you buy Kris Singh's Pagani you will forever be in Kris Singh's old car and then a Pagani. If you buy a Pagani from some guy in the middle of no where that no one knows about you will never get that type of reaction. If only the two cars were available I would choose the non one off car for the same price then a car everyone knows about because its a "special edition." Just my opinion. There's an ass for every seat.