Add AWS pricing and IAM links (#3606)

Author: imjohnbo

content/admin/installation/installing-github-enterprise-server-on-aws.md

@@ -21,6 +21,9 @@ This guide assumes you are familiar with the following AWS concepts:
  - [Using Security Groups](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-network-security.html) (For managing network access to your instance)
  - [Elastic IP Addresses (EIP)](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html) (Strongly recommended for production environments)
  - [EC2 and Virtual Private Cloud](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-vpc.html) (If you plan to launch into a Virtual Private Cloud)
+ - [AWS Pricing](https://aws.amazon.com/pricing/) (For calculating and managing costs)
+
+ This guide recommends the principle of least privilege when setting up {% data variables.product.product_location %} on AWS. For more information, refer to the [AWS Identity and Access Management (IAM) documentation](https://docs.aws.amazon.com/IAM/latest/UserGuide/best-practices.html#grant-least-privilege).
 
 ### Hardware considerations