TweakTown spotted that the HGST UltraStar He6 from Western Digital's HGST division is being sold via Amazon for $798. This is world's first helium-filled hard drive, it has a capacity of 6TB.
This new technology is currently aimed at the enterprise market, it's unknown when, or if, we'll see helium-sealed HDDs for the consumer market. The benefit of using helium in a HDD is multifold, the lower density of helium results in significantly less drag force acting on the drive's platters and also reduces the fluid flow forces buffeting the disks and the arms.
Helium-sealed HDDs can contain more platters, boosting the maximum storage capacity, while also requiring less power and lowering the heat output.