How are you getting accurate pricing for AWS components? I know Amazon's Simple Calculator uses an undocumented pricing endpoint, but that endpoint could change and become inaccurate.
However, AWS just announced a proper pricing API! Check out https://aws.amazon.com/blogs/aws/new-aws-price-list-api This will make life much easier, it does however not yet cover all services, for example ElastiCache is still missing while Cloudcraft already serves pricing for it.