Addendum
My feeling - and reason for asking for info from anyone who knows more than me
was that there are lots fo helmets out there from well over £100 down to about £15
and apart from the design and colour there seems to be very little difference
unless you include "smart" ones - some of which just have a light on them!
but this is a thing that you only really use for safety unless you are hard core and need weird aero things
but what makes it safe is the question - and all I got was marketing
very few of the ones I looked at online - and in Halford - actually mention the British or European Standard
OK, I'll chuck my two pennyworth in........and then put on my tin hat....helmet
Halfords £15 helmet ex VAT is £12.50 retail. I would suggest most retailers work on a margin if +/-40% - this is based on experience supplying independents and big box retailers.
At 40% margin Halfords paid £9 for that helmet. The manufacturer has to make profit from that sale, then there are distribution costs, fixed overheads, sales costs, labour costs all to come out of the £9.
My question would be how much of that £15 actually went into materials to protect one's head.
I wear a Kask. This is my third, of the other two the first cracked in four places, the other in two. I have no evidence but when I'm thrown threw the air after being hit by tractor driver from behind at 30+ mph........I know which helmet I put my trust in!! Yes, of course there's an element of marketing in £120 - 150 helmets but it ain't all marketing bull.