AWS Lightsail is a possible workaround for bandwidth heavy simple workloads. The smallest $3.50/mo instance (t2.nano behind the scenes), comes with 1TB outbound bandwidth - equivalent of about $90 for the same in EC2 excluding the instance cost, and bundled bandwidth increases for larger types.
I wouldn’t risk AWS closing the account.
It should work, but don’t know how would AWS view it.
"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 Services as described in the Documentation), and if you do, we may throttle or suspend your data services or suspend your account."
this. the only way I can make profit with my web service is by using a third party low budget CDN as a caching layer. Even with that, S3 data transfer remains my biggest cost.
if I could spare the time, I'd make a custom caching layer so that S3 is never hit at all except for upload, and is used only for disaster recovery.
I haven't done the math, but depending on your bandwidth requirements - you could try spinning up a couple vms at DigitalOcean/Linode/somewhere with bundled bandwidth, and then just run nginx as a cache with s3 as the backend.