My most expensive purchases are my DKNY handbag, a leather jacket and a bright pink Karen Millen dress, and I think the jacket cost about £170 (the handbag should have been £200 but was on sale). So not much by everyone else's standards.
Even if I had the money, I don't know that I would be able to drop that much on one item of clothing. Maybe if it really was absolute perfection, but even then, I'm not sure. I do follow the cost-per-wear philosophy, which is why I have no qualms about the things I did buy, but I'm a bargain-hunter by nature. I've only just thrown out a £12.99 T-shirt that lasted me over ten years, so it's hard for me to look at something that costs ten, twenty, a hundred times that, and say "well, yeah, but it'll last for ages."
That's not to say I don't get serious envy from seeing the things everyone here posts, though...