message: Extend explanation of cost savings in a CDN
diff: @@ -10,9 +10,23 @@ This document outlines why we use CDNs, for what, and how we have set them up.
  ## Objectives
  -- Reduce costs of outbound traffic by caching resources in the CDN
  -- Reduce load on origin servers to save compute resources
  -- Provide a way to rewrite legacy URLs for some resources
  +We have three goals for our use of CDNs in our infrastructure:
  +
  +1. Reduce costs of outbound traffic through cheaper pricing and caching
  +2. Reduce load on origin servers to save compute resources
  +3. Provide a way to rewrite legacy URLs for some resources
  +
  +### Reducing Costs
  +
  +As an open source project, we have to be very mindful of our infrastructure
  +costs. Outbound traffic is by far one of the most expensive items on our monthly
  +bills, and one that will continue to increase as Rust gets more popular.
  +
  +Cloud providers typically charge different rates for outbound traffic based on
  +the service. For example, serving data straight from [Amazon S3] is more
  +expensive than serving the same data through an [Amazon CloudFront]
  +distribution. This is why we now use a CDN by default, even for services that
  +can't make use of other features of a CDN such as caching.
  ## Infrastructure
  