I'm just looking for storage and it seems that the cheapest option is the WD Green 3TB drive. It is priced at $180CDN for $60 a TB. This is the absolute cheapest per TB. Its not extreamly fast and is best for just media, nothing heavy, but if all your doing is added more storage to your media server, this is the best.
Edit Nov 9th
Hard drive prices have dramatically increased due to the flood in WD's plants
Seagate has also came out with a similarly prices 3TB HDD which scores better on PC Maximums test