It's about the same thing as paying £10k for a watch that tells the time less accurately than a £30 quartz.
I can't afford the £700 jeans, I just get that there are certain brands that cost more than others in just about everything we buy. Things are worth what someone's prepared to pay.
Some of the really expensive jeans that Kerry buys appeal to me massively; I love the look of the pair he bought yesterday and posted here. But I'm a lover of Nudie jeans and I can afford those and they fit me better than any jeans I've ever owned, including those that have cost more.
Horses for courses dude.