The bandwidth costs are so far out of line with what the network transfer actually costs, it just feels like price fixing between the major cloud players that nobody is drastically reducing those prices, only storage prices.
Charging 5 cents per gigabyte (at their maximum published discount level) is the equivalent to paying $16,000 per month for a 1 gigabit line. This does not count any operation costs either, which could add thousands in cost as well, depending on how you are using S3.
There are several providers that offer a unmetered 1gbps line PLUS a dedicated server for ~600-750/mo. Providers like OVH offer the bandwidth for as little as 100/month. ( https://www.ovh.com/us/dedicated-servers/bandwidth-upgrade.x... ) I am just not sure how amazon can justify a 160x price increase over OVH or a 30x increase over dedicated server + transfer.
For the time being, the best bet is to use S3 for your storage and then have a heavily caching non amazon CDN on top of it (like cloudflare) to save the ridiculous bandwidth costs.