Image: Anthropic / anthropic.com Claude Sonnet 5 Intro Pricing Ends August 31 — Your Bill Goes Up 50% on September 1
Anthropic's introductory rate of $2/$10 per million tokens for Claude Sonnet 5 expires at the end of the month. Standard pricing of $3/$15 takes effect September 1, and the new tokenizer adds another layer of cost that most estimates undercount.
If you’re calling Sonnet 5 through the API, you have 25 days at current rates. Anthropic launched the model on June 30 with a stated intro price of $2 per million input tokens and $10 per million output tokens, and that price ends August 31. Starting September 1, the standard rate is $3/$15.
That’s a 50% increase on both input and output. For most workloads, it’s the biggest single pricing change you’ll see this year.
The tokenizer adds to the bill
The raw price numbers don’t tell the full story. Sonnet 5 shipped with a new tokenizer, and for typical developer content — code, JSON, long prompts — it counts roughly 30 to 35% more tokens than the tokenizer used for Sonnet 4.x and Opus 4.x.
That means a stable workload hitting the model the same way on September 1 as it is today faces two compounding changes at once: the rate goes up 50%, and the token count per request goes up 30-35%. The effective cost increase over an August bill can realistically be 65-80% depending on your content mix, not the 50% that the list price change suggests.
If you’ve been benchmarking costs against Sonnet 4.6 or Opus 4.x, those numbers don’t carry forward.
What you can do before the deadline
A few practical options, depending on your setup:
Audit your workloads now. Pull your July and August token counts and estimate what September costs at $3/$15. If the increase is significant, decide whether Sonnet 5 is still the right model for each use case. Haiku 4.5 ($0.25/$1.25) covers many simpler tasks at a fraction of the cost, and Opus 5 ($15/$75) is still positioned for the most demanding agentic work — the middle tier has moved up in cost but Sonnet 5’s capability ceiling also moved up with it.
Check which models your frameworks are calling. A lot of integrations set the model at configuration time and don’t get reviewed unless something breaks. Make sure claude-sonnet-5 calls are intentional, not defaults that followed from an upgrade.
Lock in August rates for batch jobs. Requests submitted through the Message Batches API before midnight August 31 PT count at the intro price even if they process on September 1. If you have large batch workloads scheduled, front-load them.
What doesn’t change
This applies to API pricing only. Claude.ai subscription plans — Pro, Max, Team, Enterprise — are not changing on September 1. The price shift hits developers calling the API directly and companies building on the Anthropic platform.
Anthropic hasn’t confirmed whether Sonnet 5 will stay at $3/$15 as the standard rate or whether further price changes are planned, though the API pricing page has historically updated several times per model generation.
Sources: anthropic.com/news/claude-sonnet-5, finopsllm.com, enterprisedna.co