A thing bothers me regarding that calculation. Shouldn’t the time it takes to write the data to all those tapes be taken into account? I.e., if you’re using tapes to transport data, your real bottleneck is your tape drive write speed.
Perhaps an artifact of the time period. In the 90's, you likely already did backups to LTO/Ultrium tapes daily. So the time was considered already sunk cost.
