I cannot see anyone that may consider paying that sort of money wanting it to be red. i think they made a mistake with the colour choice when specing to that sort of level. Maybe I'm wrong but I know i ruled it out when looking because of the colour.
I find this a bit of an odd argument. Just because
you can't see anyone paying £50k for a red car, it doesn't mean somebody won't. For every one person who won't, there's probably another who might/would.

I paid the thick end of nearly £70k for a brand new bright red RS4 back in 2015, why, because I liked the colour and didn't want the mundane Black/Grey/White default choice. I nearly paid extra for a stock Riviera Blue car, but it was a bit too out there for me when I saw it in the metal. The Riviera Blue car sold the following week, so that proves that just because I didn't want it, somebody else did.
Subjectiveness is exactly that, subjective, it has no bearing on the total cost of a car. Having said that, it's a £50k Golf, but as has already been pointed out, there are buyers out there for that car without a doubt. Cash buyers who don't care about saving a couple of grand, and people who want something different from the norm.
Some people think I'm mad for speccing a GTI to nearly £39k and they've asked the question "why didn't you buy an R instead?" The answer is short and simple, because for every one of me there's another who thinks differently.
Horses for courses
