Working at a startup that deals in large data (our storage is measured in PB), egress is the only thing thing that matters if we're going to choose a new storage provider. And an automated class management system a la S3 or GCS.
I'm always surprised to hear that folks really think about egress costs. I think that's true if you're egressing across the internet for things like photos (i.e. if I'm embedding an image stored on S3 in my website), but for most use cases -- you should store your data in the object storage system that's in the same cloud as your compute to avoid those charges and performance penalties.
We're saying the same thing, really. Basically until AWS/GCP/Azure have minimal egress fees there is no way we can switch over to a different storage provider. They obviously know this so it will probably never happen.
GCP: $0.023/GB/month (standard storage, beyond 5 GB free limit)
Azure: $0.019/GB/month (hot, first 50 TB/month)
Cloudflare: $0.015/GB/month (beyond 10 GB free limit)
Scaleway: ~$0.013/GB/month (single-zone)
Backblaze: $0.006/GB/month
Hetzner: ~$5.49/month + $0.0054/GB/month (beyond 1TB free limit)
Egress costs vary though.