The OCLC Research Library Partnership (RLP) has just released a really useful report titled "Total Costs of Stewardship: Responsible Collection Building in Archives and Special Collections", an issue taking on ever-greater importance, particularly (though far from exclusively)  in the context of digital materials. See

https://www.oclc.org/research/publications/2021/oclcresearch-total-cost-of-stewardship.html

There's also a post on their Hanging Together blog about the report at

https://hangingtogether.org/?p=8986

Clifford Lynch
Director, CNI