The Alpkit moan does seem to be making a mountain out of a molehill. If you look at the Alpkit comparison table, you'll see that:
1) It was updated back in early September, so there has been four months since those prices were current. Considering that every store in the western world has had a sale for the last couple of months, I'm not surprised that prices are generally a little lower than quoted, although often not by much. And of course the longer a piece of kit has been out, the more the cost tends to fall over the period of it being stocked.
2) The prices are RRP, and a guide only. I can't imagine too many people willing to spend £140 on a bag simply check out Alpkit, and then not bothering to look at the alternatives,as TP points out. In fact they say at the top of the page 'We do everything we can to make sure our sleeping mats offer outstanding value without compromising quality or performance, however we appreciate you may want to shop around. Here is a rough and ready chart to help get you started'. I take it from that statement that they have a certain amount of faith in their bags, and are not trying to con anyone.
You can get other bags/kit cheaper, possibly at a very good price indeed, but as Rosswm put it, 'You can get superior kit at realistic prices if you're patient & shop about'. Sometimes you get lucky, other times you don't. Alpkit is generally in the 'sweet spot' as far as price to value is concerned, and has a great rep for service and quality, as well as free delivery (£6 is not unusual to be charged, judging by a couple of websites).
If they really wanted to diss the opposition, I suspect that they would not have the weight of of a PHD as 'breathtakingly light'.
I'm just a happy customer of Alpkit (like a lot of us here), and would regard their stuff as a baseline - if you can pay the same or less for more or equal, then great. If not, you havn't lost anything.
TP has it right, ' Your first kit will not be your final kit'. But buy the best you can reasonably afford, that way you'll be warm and comfortable, and you'll enjoy whatever you want to do. After that, you get what suits, which will evolve depending on time of year, budget, etc.
I'm now tempted by the Lichfield Treklite as well (unless the Banshee 200 really comes down in price). Any reviews?