Here's a Pentax lens at big UK retailer. £629.99 ; and here it is at big US retailer $689.95, less a $100 rebate - net price $589.95. With the pound trading at $1.967, my sister in California can buy it for under £300.
Stuff costs more in the UK than the US. For example an Xbox 360 $399 (£200) in the US, and £275 in the UK. Some products have localization costs (different manuals, safety stickers, cables etc). UK dealers work to higher margins. UK distribution costs are higher. There are taxes (e.g. 8% duty on lenses) and of course VAT which alone accounts for half the difference in X-box prices, but when I'm paying more than double I feel that someone somewhere is taking the Mickey Bliss.
Some friends of ours recently started a book shop and they have been having the same thing with some books which carry the US$ price on the cover; there's no VAT on books, nothing to localize, it's margins and distribution costs. Here's a snippet from their blog.
A phonecall to the wholesaler says "we charge the full UK currency equivalent to cover the costs of getting the book over from the US" ..... How did you bring the book over from the US? In a sponsored canoe, one at a time?
"In a sponsored canoe ??! " will enter my library of phrases.