Some of the line items on my bill have the "blended" annotation on them—what does that mean?
For billing purposes, AWS treats all accounts in an organization as if they're one account. The pricing tiers and capacity reservations of the accounts in the organization are combined into one consolidated bill, which can lower the effective price per hour for some services.
This effective price per hour is displayed as the "blended" rate in your Cost and Usage Report or AWS Cost Explorer. The blended rate shown in the console is for informational purposes only. For more information, see Blended Rates and Costs.
If you're the master payer account for an organization, and you want to restrict the pricing benefit of Reserved Instances to the accounts they were purchased on, disable Reserved Instance sharing for your organization.