Helium filled HDD Cost Savings

gistfile1.txt

Cost per kWh: http://www.electricchoice.com/electricity-prices-by-state.php
GA $12.17
MA $15.86

Kilowatt = 1000 Watts
Watt = The unit, defined as one joule per second, measures the rate of energy conversion or transfer.

Press release on energy savings:
http://www.hgst.com/press-room/press-releases/hgst-ships-6TB-Ultrastar-HE6-helium-filled

"- 23 percent lower idle power per drive - 49 percent better watts-per-TB - 
See more at: http://www.hgst.com/press-room/pres-releases/hgst-ships-6TB-Ultrastar-HE6-helium-filled#sthash.EGMJomwt.dpuf"

Power requirements of HDD: 6.5 to 9 W
http://www.buildcomputers.net/power-consumption-of-pc-components.html

max kWh = 43829.1 (hours in 5 years) x 9 (Watts) / 1000 = 394.4619
394.4619 x 12.17 (Cents / kWh) = 4800.601323

$48 in GA over the lifespan of the drive assuming maximum throughput for 5 continuous years (worse case scenario)
$62.56 in MA

51% less energy usage:
$24.48 in GA
$31.90 in MA

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Dimensions of a 3.5" HDD:
4 in × 1 in × 5.75 in (101.6 mm × 25.4 mm × 146 mm) = 376.77344 cm³ = 0.013278 ft³

Density of Helium: 0.0001785 g/cm3
http://wiki.answers.com/Q/What_is_the_density_of_helium?#slide=2

Cost of Helium: $3 / ft³
http://www.phys.ufl.edu/~cryogenics/hecost.htm

0.013278 ft³ x $3
Cost to fill a HDD with Helium: $0.039 (minus negative space for components)

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Conclusion: It will cost manufacturers $.03 cents per HDD to fill the volume with Helium. 
The maximum savings on energy of the HDD under full load for the lifespan of the drive will be about $24 in Georgia, $31 in Massachusetts. 
The savings to the consumer will be determined by the markup of a Helium filled drive.