This is one of those dates that’s easy to miss — until the next invoice lands. The introductory price for Claude Sonnet 5 expires on August 31. From September 1, standard pricing kicks in, and it’s got some weight to it.
What actually changes
Right now, under the intro tier, you pay 2 dollars per million input tokens and 10 dollars per million output tokens for Sonnet 5. From September 1, that becomes 3 dollars input and 15 dollars output. That’s a clean 50 percent increase — on both sides.
Sounds like a simple price bump. But there’s a second effect that’s easy to overlook: the new tokenizer. Sonnet 5 counts roughly 30 percent more tokens for the same text than Sonnet 4.6 did. And because you pay per token, that adds up. For some workloads, the effective cost jump ends up not at 50 percent, but beyond it.
Why this is more than a footnote
At launch, Anthropic positioned Sonnet 5 as largely cost-neutral — and during the intro window, that held. September 1 is the moment that math gets redone. If you run Sonnet 5 in agents, pipelines, or background jobs where tokens flow through at scale, you’ll feel the difference most.
My take
Honestly, I find news like this almost more important than the next shiny feature — because it hits your costs directly, not just your options. So the advice is deliberately low-key: use the three weeks until the end of August and look at your actual usage. Where is Sonnet 5 running, where would a smaller model do, and where is the full price genuinely worth it?
This isn’t fearmongering — Sonnet 5 stays a strong model, and 3 dollars input isn’t an outlier by market standards. But a 50 percent price jump plus a tokenizer effect is exactly the kind of change worth working through once, consciously, instead of discovering it on your September bill. And the trend toward intelligent routing — automatically sending each task to the cheapest capable model — gets a fresh tailwind from deadlines like this one.
Sources: FinOps LLM: Sonnet 5 Intro Pricing Deadline, Finout: Sonnet 5 Pricing 2026