This is pretty insane. For under $2000 - excluding cost of hard drives - you can build a STORAGE POD 3.0. A total cost of $10,717.59 when using 4T drives - which comes out to a $0.0595 cost per GB.
UPDATE: Don't want to build yourself? You can order a pre-built unit - tested and ready to go - without the hard drives for $5395 - $80 more to have a custom logo on the case and $50 more for a custom color. Order from 45drives.com.
UPDATE: 45Drives Wiki
UPDATE: Interesting not on filesystem used by Backblaze -