Simplistic Assumptions: Your Physical Agents with Support costs $12.5K over 5 years and your HP MSL 4048 Tape Array costs $15.7K over 5 years. Each LTO Tapes costs $25. Iron Mountain Costs are assumed to be $1/per tape and includes the monthly Iron Mountain Service Costs
Simply: if you have 1 array, your break even point with a majority of Cloud Based systems in which price their Archive based tiers to about $1-4 / TB / Month, you would have to back up at least 500 – 600 TB comparably to make it worth it. Although, it does not include the labor costs related to having to physically load and unload a tape system. Although, if you have 3 offices your break even point would be 300 – 400 TB comparably at the low end and about ~ 1.5 PB at the end high end to make it cost competitive with cloud based systems.