The deal can be accessed here, and requires the coupon code EMCWXXT68. The coupon expires on Oct. 9. Shipping is free after the coupon is applied. Newegg.com charges sales tax in California, New Jersey, and Tennessee.
HGST, for those unaware, is a Western Digital company, which should give customers confidence in the drive's reliability. HGST was formerly Hitachi Global Storage Technologies. That company was founded in 2003 as a merger of the hard disk drive businesses of IBM and Hitachi. On March 8, 2012, Western Digital acquired Hitachi Global Storage Technologies for $3.9 billion in cash and 25 million shares of common stock then valued at approximately $900 million.
For comparison, the HGST Touro Desk Pro 4TB USB 3.0 Black External Hard Drive sells for $172.35 at Amazon.com, but isn't currently available directly from the company. Nor is it available via :"Fulfilled by Amazon.com." That means, unfortunately, no free Prime two day shipping for Amazon Prime members.
A bonus is the fact that the drive has a 7200 rpm rotational speed. Many of these high capacity external drives ship with 5400 rpm rotational speeds. As a another bonus, the drive ships with a USB 3.0 port. A number of external drives continue to ship with the slower and older USB 2.0 standard.
As a comparison, USB 2.0 was released in April of 2000. The maximum signaling rate of USB 2.0 is 480 Mbit/s; effective throughput is "up to" 35 MB/s or 280 Mbit/s. With the advent of USB 3.0, the USB 2.0 standard is now called "Hi-Speed."
Meanwhile, USB 3.0 was released in November of 2008. It has received the new "SuperSpeed" mode labels and has a signalling rate of up to 5 Gbit/s and a usable data rate of up to 4 Gbit/s. It is backwards compatible with USB 2.0, as you would expect, but lags in speed behind Apple's Thunderbolt I/O.
To address that, a January 2013 press release from the USB standards group revealed plans to update USB 3 to 10 Gbit/s to put it on par with Apple / Intel's Thunderbolt I/O port speed by mid-2013. It's unclear when USB 3.1 will reach the market, though.
The slow adoption of USB 3.0 -- evident by the proliferation of devices still being released with USB 2.0 capability -- will probably mean a similar slow adoption for USB 3.1, in any case.