Why is DDR more expensive than DDR2?

I've got 1GB of RAM in my Dell Inspiron 9200, and I could do with a little more memory, especially when running a Virtual Machine along with any other applications on the host OS, which is XP Pro.

When I got my machine 1GB was a good choice, any more than that and DELL would have charged me as much as the price of the laptop again. Unfortunately this memory is configured as 2 512MB SODIMMS, so I'll have to ditch at least one of the modules in order to upgrade.

I got an email from a well known memory supplier this morning and it was offering a discount of £5 on any order over £50. While the discount offer isn't that attractive, I thought I'd check out the current prices anyway.

DDR 1GB SODIMM, £51.69 Including VAT.
DDR2 1GB SODIMM, £14.09 Including VAT.

This price difference seems rather unfair to me and two thoughts sprang to mind. Is DDR memory in short supply due to increased demand resulting from old spec machines sold with Vista or has the manufacturing focus moved onto DDR2 and DDR3 meaning DDR production levels are greatly reduced.

I had a chat with a sales agent from the company and he stated that "as DDR is much older, they have less of it in stock and that's why the prices are higher".

hmm, perhaps I'll just leave it and think about when I replace my current laptop.