Alright, so we're all constantly told the cloud is cheap and scalable. Then you get your first bill with a line item for "Data Transfer OUT From Internet" that looks like it could fund a small startup. That's egress.
In simple terms, egress is the data *leaving* a cloud provider's network to go somewhere else—like to your users, to another cloud, or back to your own data center. Ingress (data coming in) is usually free. The asymmetry is… a business model.
Why does it cost so much? Because it's a classic lock-in tactic, dressed up as a "network usage fee." They've built a fantastic walled garden with great services (compute, storage, DBs). Egress fees are the toll on every road leading *out* of that garden. Want to move your 100TB database to another provider or offer a download? Get ready to pay.
* It's priced high enough to make you think twice about multi-cloud or repatriation. Suddenly, that "cheap" object storage isn't so cheap if you need to actually *use* the data elsewhere.
* The pricing is often opaque and cascades. Egress from a VM in US-East-1 to the internet? That's one fee. Egress from that VM to an S3 bucket in a different region? That's *two* transfers (VM -> S3 cross-region, then S3 egress if downloaded), both billed.
They'll give you technical justifications about network maintenance and capacity planning, but let's be real: it's a profit center and a retention strategy. The bigger your data footprint, the more expensive it becomes to even consider leaving.
Trust but verify.