Cloud bills grow for structural reasons, not careless ones. Environments outlive their projects, instance sizes are chosen defensively, and nobody owns the total. Adding an approval gate solves none of that; it just slows delivery down.
Make ownership unambiguous
Tagging enforced at provisioning time is the single highest-return control. Every resource carries an owning team, an environment and a cost center, or it does not deploy. Once spend can be attributed, most optimization happens without central intervention.
Publish showback before chargeback
Teams respond to visibility faster than to invoices. A weekly showback report against a team's own budget produces meaningful reduction long before any cross-charging mechanism is implemented.
Pave the efficient road
If the golden pipeline provisions right-sized, auto-scaling, auto-expiring infrastructure by default, engineers get the efficient outcome by doing the easy thing. Governance that relies on discipline erodes; governance built into the default path does not.