Well - rich people want to distinguish themselves from us ordinary folks by paying high prices.
This is not a bad thing at all. It keeps the flow of money up and running.
Many rainwear and fetish garments from the usual fetish designers often look even better and more elegant than those from famous high-fashion designers. Just my opinion.
I just read the description. It is not actually a raincoat but a leather coat. It sais patent leather. Don't know how well this would cope with rain.
Being me I wouldn't mind testing its suitability for rain, mud etc if someone would offer me one of them for testing.....