Though Glacier is hooked to S3 (for obvious reasons) I don't think it's relevant to a discussion of bandwidth egress costs. If you're frequently pulling things out of Glacier then you're using it wrong.
I agree! Most conversations that somehow talk about GCS being more expensive usually are "oh actually, AWS just charges less for egress" (which isn't a non sequitur but is effectively orthogonal). Again, I'd respond directly if the site weren't hugged to death :).