In reply to simes303:
Whilst I respect your ability to manufacture your own gear for a fraction of the cost, the long and short of it is that you represent an impossibly small minority of people willing to engage in this level of effort. Most people - rightly or wrongly - just want to buy stuff.
I would also argue that it shouldn't really come as a surprise given that this quite unashamedly premium product. If you want to spend less buy a Karrimat, but be prepared for it to be quite cold/uncomfortable; if you want to spend a bit more, buy a Thermarest; but if you're after something that is super specialist, super warm, then - on account of Dan's feedback - the Aerostat is a strong contender.
Also, having had a quick scan around the competition it would actually appear to be quite competitively priced, with the DownMat HL Winter M coming in at £205, the Thermarest Neo Air XTherm coming in at £195, and the Sea to Summit Comfort Plus at £175 - all of which were reviewed in last year's group test (https://www.ukclimbing.com/gear/camping/sleeping_mats/insulated_inflatable_...).
In summary, if you are looking at buying a premium product in any given area you'd expect to pay a premium. Whatever you think about that cost a quick analysis of what's out there suggests that the £170-£195 mark is about what you'd expect to pay. If you're after something cheaper there's plenty of options out there, just don't expect them to be quite so warm.
Post edited at 11:14