I wondered this, so I went to John Lewis and priced up how much it would cost for a length of ivory tulle (long enough for a chapel-length veil with a bit to spare in case of mistakes) and plenty of Swarovski crystals to sew onto it. Allowing a small cost for comb and sewing materials I estimated it would cost about £50 for me to make it myself! To be fair most of this was the price of the crystals (£35 for 100) but that goes some way to explaining the expense. In the end I've decided I will probably buy mine from UK Wedding Veils as it will cost just over £60 for the same thing. I think the bridal shops put a huge mark up on them plus they generally have to be ordered from abroad.
I was just going to post the same. £35 for 100 crystals is very expensive.