The best cloud architects I've worked with can tell you what their design will cost before a single resource is deployed. That sounds obvious. It's surprisingly rare.
Plenty of high-level designs sail through approval with no number attached. The diagram is elegant, the technology choices are defensible, and the running cost becomes someone else's problem three months later when the bill arrives. A design without a cost is half a design. It tells you what you'll build without telling you what you're committing to.
Owning the number changes the work in a few ways.
It forces honest trade-offs at the whiteboard, when they're cheap to make, instead of in production, when they're expensive and disruptive. "Do we actually need the premium tier here?" is a five-minute conversation on paper and a migration project once it's live.
It hands the business a real figure to decide on. "Here are three shapes of solution, at roughly £8k, £14k and £22k a month, and here's what each one buys you in performance and resilience" is a decision a director can actually make. "It depends" just postpones the decision.
And it puts accountability where it belongs. An architect who priced the design owns the outcome, which tends to produce more conservative, better-justified choices than one who hands over a diagram and walks away.
Pricing a design well comes down to a few unglamorous tools: the Azure pricing calculator, a sizing model per environment, and honest assumptions about growth and data egress, written down where they can be challenged. The number will move, and that's fine. A figure with stated assumptions is something you can review and refine. A blank space is not.
For a leader, the ask is simple. When a design lands on your desk, ask what it costs to run, and ask what that number depends on. If your architect can design it but can't price it, you're carrying a risk you can't see yet. A good one will already have the figure, and will be glad you asked.
Next: more on turning solid architecture into decisions the business can actually make.