It's almost as cheap as Glacier, but requires no waiting and has no complicated hidden costs, just simply somewhat higher request pricing, a minimum 30 days of storage and an extra $0.01 per GB for data retrievals.
> Standard - IA has a minimum object size of 128KB. Smaller objects will be charged for 128KB of storage.
Rounding up all small files to 128 KB can be a huge deal. I for example use Nearline to directly "rsync" my NAS box for offsite backup (yeah I know, I should use something that turns it into a real archive or something, but I'm lazy and Synology has this built in). If those hundreds of thousands of (often) small files were rounded up, S3-IA would easily be more expensive than S3/GCS.
Disclaimer: I work at Google on Compute Engine and am a happy Nearline customer myself.
You can also try the duplicity backup tool. It uses tar files to store the primary backup and its binary incremental deltas. It supports a number of backup back-ends, but you can also just generate the backup to a local disk and then rsync it to a remote location.
It's almost as cheap as Glacier, but requires no waiting and has no complicated hidden costs, just simply somewhat higher request pricing, a minimum 30 days of storage and an extra $0.01 per GB for data retrievals.