We had a legal requirement to be able to product up to 7 years worth of bank statements upon receipt of a subpoena.
Not "reproduce the statements from your transactions records" but "give us a copy of the statement that you sent to this person 6.5 years ago"
We had operational data stores that could generate a new statement for that time period, but if we received the subpoena then we needed to be able to produce the original, that included the (printed) address that we sent it to, etc.
We had (online) records of "for account 12345, on 27th October 2011, we sent out a statement with id XYZ", we'd just need a way to pull up statement XYZ.
There's no way(^) we'd ever get subpoenaed for more than 5% of our total statement records in a single month, so something like Glacier would have been a great fit.
We had other imaging+workflow processes where we'd receive a fax/letter from a client requesting certain work be undertaken (e.g a change of address form). 90 days after the task was completed, you could be pretty sure that you wouldn't need to look at the imaged form again, but not 100% sure. We could have used glacier for that.
We use case that would have cost us (rare, but we needed to plan for it) was "We just found that employee ABC was committing fraud. Pull up the original copies of all the work they did for the 3 years they worked here, and have someone check that they performed the actions as requested." Depending on circumstances & volume that might trigger some retrieval costs, but the net saving would almost certainly still be worth it.
(^) Unless there was some sort of class action against us, but that's not a scenario we optimised for.