Earlier quoted context omitted.
https://aws.amazon.com/service-terms/ > 51.3. You may not use Amazon Lightsail in a manner intended to avoid incurring data fees from other Services (e.g., proxying network traffic from Services to the public internet or other destinations or excessive data processing through load balancing or content delivery network (CDN) Services as described in the technical documentation), and if you do, we may throttle or suspe…
At least AWS is fully aware how premium their normal data transfer is and that one might want to optimise those costs.
It takes very low hitrates before it pays for itself several times over including management overheads.
Sometimes you can justify a complete replica outside AWS (one of the things I will gladly pay AWS for is durability)