I'm trying to use the nomenclature from the Glacier pricing page, where "transfer" is the verb to reference the cost per GB downloading the data from the remote provider. Glacier has an additional "retrieval" cost per GB that B2 and others do not (because they most likely have to physically retrieve a tape/HDD drive with your data on it).

https://aws.amazon.com/glacier/pricing/

https://www.backblaze.com/b2/cloud-storage-pricing.html

Sorry I don't get it. With B2 I have to pay if I want to say download 100GB of data in B2. From what I read, you say this isn't so. But the pricing page state otherwise

B2 has 2 charges: $/GB to store the data, and $/GB to download it (uploading to both is free)

Glacier has 3 charges: $/GB to store the data, $/GB to retrieve the data from "cold" storage, and $/GB to download it.

Retrieval !== downloading ("transfer"). Retrieval is an additional cost to downloading ("transfer").