It is absolutely mind blowing to me that you can purchase that amount of storage with 20% to spare for around $500 these days. 12TB, $498 : http://www.amazon.com/Red-Desktop-Hard-Disk-Drive/dp/B00LO3K...
http://www.tapeandmedia.com/quantum-lto-6-tape-ultrium-tapes...
The drive isn't cheap though, but tape is still the cheapest media for long-term archival storage.