Only Actual Cost is used to generate Recommendations / Rightsizing for EC2 and EBS.
Cost savings is compared only with Actual cost because many customers observed that using List Price (the standard on-demand rate) for comparisons often inflated the perceived savings, especially when organizations already benefit from discounts such as Reserved Instances (RIs), Convertible RIs, or Savings Plans.
Also the Actual cost shows recommendations and savings based on the real amount paid after discounts, reflecting your organization's specific pricing agreements and usage patterns