A good crash helmet is worth its weight in gold. I don't buy the "if you've got a ten dollar head, get a ten-dollar helmet" argument. With all the certification processes both in Britain and in the EU, I doubt it's possible for an unsafe helmet to get to market these days. Even the cheap ones look good now. What you pay for in a good one is comfort and general useability - a lining that won't feel and smell like a dog's bedding after two months, a visor that resists misting-up, ventilators that work, good wind noise reduction, and so on. I don't mind spending money on something that is going to make my riding more comfortable and pleasant.
I have four helmets currently. The main everyday helmet is a Shoei XR1000, like this:
It's reasonably quiet, it has excellent anti-misting performance (important to me, as I breathe a lot) and it's comfortable even over a whole day. It should have cost me around £350, but by accepting last year's graphics (who cares?) I got it for just over £200. I also have a cheapo open-face helmet (hardly ever worn, but there for the days I want a slow ride out wearing shades), a £99 full-face Caberg that I bought when I got back into biking a few years ago, which is OK-ish and would do at a pinch if the Shoei ever got damaged, and a mega-cheap flip-front lid from Lidl. I think that one was under £40. I got it to see if I liked the flip-front idea. I used it once. It's awful.
I came across a site with some remarkable helmet graphics which I thought I would post for a laugh. Of course, we have all seen Rossi's superb effort:
And this one made me laugh too.
And not to forget the fantastic Geoff Duke: