If you pay more than 20% of the advertised rates of AWS bandwidth, you're being robbed. 10% or less is doable.
If you need durability guarantees, consider if the cost problem is storage or bandwidth. If the problem is bandwidth costs (in other words: your data set is small and accessed often), store at S3 or Backblazer or similar, and place a server or two at a cheap bandwidth host with Nginx and aggressive caching policies.
I've done this for a couple of customers who did not trust other data storage options with their data, and you can rent a server + multiple TB of transfer for a fraction of a the cost of 1TB transfer from S3....
Look into IPFS, interplanetary file system. You still need machines to serve files. However, the system has some definite advantages:
1. A file/directory is referred to its immutable hash.
2. A request for a specific hash is made to the network, not a single machine.
3. All machines that have that hash can swarm-download, like bittorrent
4. All communication is point-to-point encrypted
5. For backend, you can mount IPFS directly to the file system, via /ipfs and /ipns
I really wish more people knew about them. They are great.