My (peripheral) experience is that it is much cheaper to get data in than to get data out. When you have the amount of data being discussed — "Enterprise data. Going back years." — that can get very costly.
It's the amount of data where it makes more sense to put hard drives on a truck and drive across the country rather than send it over a network, where this becomes an issue (actually, probably a bit before then).
AWS actually has a service for this - Snowmobile, a storage datacenter inside of a shipping container, which is driven to you on a semi truck. https://aws.amazon.com/snowmobile/
> Q: Can I export data from AWS with Snowmobile?
>
> Snowmobile does not support data export. It is designed to let you quickly, easily, and more securely migrate exabytes of data to AWS. When you need to export data from AWS, you can use AWS Snowball Edge to quickly export up to 100TB per appliance and run multiple export jobs in parallel as necessary. Visit the Snowball Edge FAQs to learn more.
It's the amount of data where it makes more sense to put hard drives on a truck and drive across the country rather than send it over a network, where this becomes an issue (actually, probably a bit before then).