I assume that there was an initial discount period that has now expired, so I did a Google search to investigate. I didn't find anything relevant, but I did come across a sponsored link from SoftRetailer.com:
Clicking through to their website, they're offering the Ultimate version for £129:
They say that this is a special promotion until February 28th: that would fit my theory about the initial discount period, and it's plausible that Microsoft have just raised the prices a few days earlier on their EPP site. Anyway, that's cheaper than Amazon, even though it's not an upgrade version, so I put in an order with them. I got as far as the PayPal page, and then I got a bit suspicious:
The email address looks like a freebie (throwaway) account rather than being registered to their own domain. However, I'm mainly just concerned that this is too good to be true. So, I did a search for the company name, and found this discussion:
Issues with softatlantic / softwarediscountzone
Apparently this company is based in China, and they are sending out conterfeit disks. So, I've cancelled that order, and I'll go with Amazon instead.
I don't have proof that this company is dodgy; I'm just relying on anonymous people on the internet. So, it's possible that this really is a good deal, that some of you may want to take advantage of. However, you may also prefer to err on the side of caution. The main thing that surprises me about all this is that Google are happy to keep running the sponsored link after people have complained. If SoftRetailer are in fact dodgy, that does rather tarnish Google's "We're not evil" image.