A practical guide to choosing usage units, designing spending limits, and explaining AI costs before, during, and after the work.Every AI response has a price. People often discover it only when a limit hits or a bill arrives.A quick edit and a long-running agent can look almost identical in the interface. One finishes in seconds. The other might read hundreds of files, call external tools, and retry steps along the way. Yet both start with the same button.Meanwhile, AI products keep changing what they charge for: requests, credits, tasks, usage allowances. Showing more technical numbers won’t make those costs easier to understand. People want to know what a job might use, whether it’s worth running, and what they can do to spend less.For designers, that comes down to two decisions:The unit: what users see themselves spending.The moment: when they understand the cost — before, during,...