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」。
以往是優先用在自己帳號，但如果有剩的話可以挪去其他帳號用。這樣雖然比較省錢，但有時候會造成帳務的「困擾」：
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.
現在則是可以關掉：
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.
也可以分開設定：
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.
這樣雖然會比較貴，但這其實反應到某些組織文化上的問題啦...
