Unless you're going to be doing pretty much entirely sequential reads of entire files, I don't think this is likely to work well for you. B2 (and other cloud storage) isn't just priced by bandwidth but by "transactions" (requests).
It's true, there is a price for some API requests, but it's actually quite low if you're using the cloud storage to populate a local cache! Backblaze categorizes download as a "class B" transaction with 2500 free per day and $0.004/10k. I fully admit it's not a suitable solution for many workloads, but I've been playing with a VM using B2 as slow additional disk (as an additional volume, not suggesting putting / or /usr..) and am yet to exceed the free tier.
So are you actually running a VM image somewhere and using B2 as a virtual disk drive from it?