現在 AWS 讓你可以設定，是否允許 Reserved Instance (RI) 跨帳號使用：「Customize your organization’s AWS credit and Reserved Instance (RI) discount sharing using new billing preferences」。
Historically, AWS has maximized customer savings by applying credits and RI discounts first to the account that owned the credit or RI lease and then distributing the remainder, if any, to qualifying usage incurred by accounts in the same organization. While this approach had the potential of lowering the overall bill, customers were unable to control if, and how, discounts were applied across organizational lines.
To provide greater flexibility, customers can now disable AWS credit sharing across all accounts in their organization. This ensures that only the account that owns a credit, or has previously redeemed a credit, receives the associated benefit.
You can also designate a set of accounts for which RI discount sharing is disabled, while continuing to share RI discounts among the rest of the accounts in your organization.