[couterSpell]

Intuitively there is some cost for retrieval. Otherwise you'd just use the cold storage to store everything.

[tpetry]

Like every cloud storage file access costs money, so the operation to access it. But its so minimal its basically non existent for a backup solution.

[votepaunchy]

Nearline and Coldline have a per-byte retrieval cost in addition to the increased-but-still-low cost per operation.

https://cloud.google.com/storage/pricing