The Pricing Calculator is the correct choice because it enables users to build cost estimates for different service configurations before actual purchase or deployment. It helps in projecting and managing expenses by simulating various deployment scenarios, which aligns with the requirement of the business described in the question. The other tools mentioned do not serve the purpose of cost estimation: CloudTrail is for tracking user activity and API usage across accounts; CloudFormation is for infrastructure as code to model and provision resources; and IAM Access Analyzer is for analyzing access permissions to ensure secure resource sharing.