Sounds like you're looking for CloudFront. I run a site with similar usage to yours (at least on the upload side), and I see about $6 in S3 charges and another $8 for CloudFront each month.
As the grandparent said, I just can't see why anybody would spend even a minute thinking about rolling their own CDN on their own servers for anything but the most extreme use cases. It's a solved problem, and it's ridiculously cheap.
As the grandparent said, I just can't see why anybody would spend even a minute thinking about rolling their own CDN on their own servers for anything but the most extreme use cases. It's a solved problem, and it's ridiculously cheap.