The gold color seems unreasonably ostentatious, I mean, how many times do you see a car painted a golden color? Not often, it's too far out. People would be more embarrassed having a golden-plated car than feel good about it as if it's signaling wealth.

So, I expect the demand for golden iPhones to be high only in very specific subsets of people, not among normal people trying to signal a high status. People also want to signal class in addition to wealth.