I know Amazon prices aren't exactly perfect for enterprise storage costs, but they imply tape is at least 4x cheaper (assuming you are using enough to amortize the cost of the tape drive):
EDIT: Commenter below points out this 6.25TB tape is actualy 2.5TB physical -- still cheaper, in terms of $/GB, but not the 4x I mention above -- closer to 2x.
LTO-6 (what you linked) is not 6.25TB, itβs 2.5TB, despite what Amazon says.
Then add the operational costs, which is the hard part, because the operational costs for a tape are very different from the operational costs for a hard disk.
That's an apples-to-oranges comparison. The "6.25TB" number for LTO tapes is assuming a fairly arbitrary 2.5:1 lossless compression ratio. The actual data capacity of the tape is only 2.5TB.
6.25TB tape is $28 : https://www.amazon.com/HP-HEWC7976A-Ultrium-6-25TB-Cartridge...
6TB HDD is $120 : https://www.amazon.com/Seagate-Expansion-Desktop-External-ST...
EDIT: Commenter below points out this 6.25TB tape is actualy 2.5TB physical -- still cheaper, in terms of $/GB, but not the 4x I mention above -- closer to 2x.