"fraction of the cost" - how do you figure? Or are you just saying from a cost-to-store perspective?
Your Egress prices are quite a bit more compared to CloudFront for sub 10TB (.12/GB vs .085/GB).
The track record of s3 outages vs time your up and sending Egress seems like S3 wins in cost. If all your worried about is cross region data storage, your probably a big player and have AWS enterprise agreement in place which offsets the cost of storage.