TPU noticed that Western Digital has launched its 4TB 3.5" WD Green HDD. It's priced around $170 - $190, depending on what package you choose.
Designed for personal desktops that need energy-efficient, high-capacity storage, the drive offers 4000 GB of unformatted space, which should yield about 3.6 TB under a Windows NTFS file-system. Built in the 3.5-inch form-factor, the drive features SATA 6 Gb/s interface, variable sub-6,000 RPM spindle-speeds, 64 MB cache, and acoustics management. When spinning and idling, the drive is designed to draw about 3.3W, which goes up to 4.5W under stress, and just 0.4W, when the drive is parked and spun-down.