COST 9. Did you consider data-transfer charges when designing your architecture?
Ensure that you monitor data-transfer charges so that you can make architectural decisions that might alleviate some of these costs. For example, if you are a content provider and have been serving content directly from an Amazon S3 bucket to your end users, you might be able to significantly reduce your costs if you push your content to the Amazon CloudFront CDN.

Remember that a small yet effective architectural change can drastically reduce your operational costs.
Best practices:
 Use a CDN
 Architect to optimize data transfer (application design, WAN acceleration, etc.).
 Analyze the situation and use AWS Direct Connect to save money and improve performance.
 Balance the data transfer costs of your architecture with your high availability (HA) and reliability needs.