Network egress is a lock-in tactic for public cloud providers
Public cloud providers charge an extra fee for moving data out of their respective networks. This means that, once data is in, it becomes uneconomical to apply any services to that data that are not of the local cloud provider, as you would incur the egress cost as the data moves out. This also makes one-time migrations extremely expensive, to the point where the cost of data egress can overwhelm whatever near or long-term cost advantages the new platform might have.
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An App Distribution Network in Practice