Volume pricing is one thing, but look at the margins at your LBS or even online. I've got a dealer catalog for the US, and the markup on parts and accessories is not a lot compared to what I see here in Australia. For instance, I bought some SRAM gear in the US for about US$10 over dealer cost. After shipping, duties, GST, and the various distribution markups, the same parts over here are marked up an extra US$176 dollars. Holy crap! I had to check my math, as that didn't seem right, but it is. I did all my math in US$ as well.
Converted, it costs about AU$138 to buy, and the dealers sell them for $380. And that, my friends is why I don't have a real job. I cut out half the LBS profit, and make a decent packet of money.
I've checked UK prices and they suck too.