Cost management default account

Cost Management works at all scopes above resources to allow organizations to manage costs at the level at which they have access, whether that's the entire billing account or a single resource group.
Although billing scopes differ based on your Microsoft agreement (subscription type), the Azure RBAC scopes don't.

The scope that a user selects is used throughout Cost Management to provide data consolidation and to control access to cost information.
When using scopes, users don't multi-select them.
Instead, they select a larger scope that child scopes roll up to and then they filter-down to what they want to view.

The organization's default cost group is seeded when you install Cost Management.
This is a multiple organization (multi–org) cost group and is used as the default in organizations that have a Costing Method of Average and the CST: