I have been observing the cost of 1TB* 3.5" SATA disks over the last 3-4 months with the same supplier, and prices are undoubtedly on the way down again.
A WD 1TB disk that cost me £45 (ex. VAT) 18 months ago rocketed to over £115 (ex. VAT) in November 2011 and is now back to £70 (ex. VAT). Still considerably more than I would want to pay, but I intend to go for 2TB disks anyway for my next project.
I've noticed that a lot of vendors are showing this re-adjustment as a "sale" reduction.
SD
* because I've got a reference of a previous purchase