It being low level is not an excuse for systems that lead people down the wrong path.

And the traffic never even reaches the public internet. There's a mismatch between what the billing is supposedly for and what it's actually applied to.

> do you expect AWS to show you different meters for billed and not-billed traffic, but performance still depends on the sum total of the traffic (S3 and Internet egress) passing through it?

Yes.

> How is that not confusing?

That's how network ports work. They only go so fast, and you can be charged based on destination. I don't see the issue.

> It's also besides the point that not all NAT gateways are used for Internet egress

Okay, if two NAT gateways talk to each other it also should not have egress fees.

> some kind of implicit built-in S3 gateway violates assumptions

So don't do that. Checking if the traffic will leave the datacenter doesn't need such a thing.