Bandwidth is dirt cheap outside of the Cloud, e.g. I'm getting 30 TB of bandwidth as part of my 64GB RAM / 500GB SSD / Quad-Core i7 Skylake for €39 /mo (https://www.hetzner.de/us/hosting/produkte_rootserver/ex41ss...). Which roughly equates to €0.0009 /GB that also includes the cost of hosting entire server with resources that would cost an order of magnitude more on AWS/Azure.
Enterprise level network equipment and infrastructure are extremely expensive. Unusually cheap BW rate usually means cheap equipment or over-subscription or not enough qualified support personnel. And in some cases under-selling to get penetration to a market.
The reason Google Fiber can sell cheaply because (AFAIK), in almost every town or cities that they deployed their network they negotiated special deals with municipalities or equivalent entity to get free access to existing infrastructure or get special deals. There is a reason why Google Fibre is not everywhere or they are not pushing it very aggressively. Because building networks are freaking expensive even for google.
BW may not have any value but building the network and maintaining it to serve you BW is expensive. Your BW cost is a reflection of the cost of your network.
Disclaimer: I own an ISP.
I am not sure if that is entirely true. At least, Google owns the fibers between any 2 google data centers. It is probably only the last-mile that needs municipality support.
Yes, you're getting cheap pricing from an oversubscribed line.
AWS only kind of makes sense until your bill starts approaching that of a full time engineer's salary. Then you can slash costs like crazy by rolling your own infrastructure (at higher risk of downtime). Or pull a Netflix and negotiate wholesale prices.
At least you can leverage Digital Ocean, Linode, etc to run varnish caches to offload bandwidth for things like static assets while keeping your main workloads on AWS. You can build this sorta thing in a couple days I'd say.