Is Claude Opus Worth It? Claude Opus vs Sonnet Compared

Claude Opus 5.5 is Anthropic's model for complex work that needs careful judgement. Claude Sonnet 5.5 is the faster, cheaper model for well-scoped everyday tasks.

Those are Anthropic's own words. Its Sonnet 5.5 launch page calls Sonnet "a faster, lower-cost complement to Claude Opus 5.5". It says Opus is "built for complex work requiring careful judgment", while Sonnet is "strongest at well-scoped everyday tasks". Opus 5.5 came out on 22 September 2026 and Sonnet 5.5 followed on 28 September.

Under the hood they share a lot. The models overview lists a 1M-token context window, 128K-token maximum output and a June 2026 knowledge cutoff for both. A token is a small chunk of text, a little over half a word. It's the unit you pay for. The real differences are price, speed and how each one handles long, messy work.

On paper, Opus 5.5 costs twice as much per token, runs slower and wins hard tests by a few points. Prices below are Anthropic's API list prices in US dollars per million tokens, checked on 2 October 2026.

The prices come from Anthropic's pricing page. Cached input costs the same US$0.20 on both, which is easy to miss. So if your job re-reads the same long document again and again, the gap between them shrinks.

For a job that runs hundreds of times a day, the bigger model can cost hundreds more a year. For a job that runs a few times a month, the gap is cents.

Here's a worked example of an AI automation at list price, assuming both models use the same number of tokens. It sorts 200 emails a day, about 6,000 a month. Each email takes about 2,000 tokens in and 300 tokens out. That's 12 million tokens in and 1.8 million out a month.

Running the bigger model on that job costs about US$504 a year for no better result. Now take a monthly report with 50,000 tokens in and 3,000 out. On Opus it costs about 26 US cents, and on Sonnet about 13 cents. Paying 13 cents more for a sharper read is an easy call.

Claude Opus earns its cost when the job is long, open-ended and hard to check. A weak answer there is expensive to catch. Anthropic says Claude Opus 5.5 "remains clearly stronger at complex, open-ended work requiring sustained judgment".

Anthropic's Opus 5.5 page says Claude Opus is "particularly good at long and sprawling jobs like codebase-wide migrations and audits". Its product page also lists financial analysis of dense filings, and reading documents, charts and screenshots.

For a small business, Claude Opus is the model for building things. Designing a workflow, reading a 60-page tender or untangling a messy spreadsheet are all Claude Opus jobs. At UnderCurrent Automations we use Claude Opus to build workflows for Australian businesses. One bad design decision costs hours of rework later, and that never shows on your Claude bill.

Sonnet is the better buy for any job that repeats all day and has a clear right answer. Sorting email, drafting replies to new leads and pulling fields out of invoices all fit.

The Sonnet 5.5 launch page shows how close the two have become. On Anthropic's GDPval-AA v2.1 test, Sonnet 5.5 scored 1844 against 1846 for the bigger model. Anthropic also says Sonnet 5.5 "runs 30%+ faster" and "costs up to 30% less for most work" than Sonnet 5. Speed matters when a customer is waiting on a reply.

We run our own inbox sorting workflow on Sonnet. A smaller model misread too many emails, and Sonnet gets them right. Reading every email with Opus would double the bill for the same labels. Anthropic's guide to choosing a model lists Sonnet 5.5 for "everyday coding, agent, and enterprise workloads".

We pay for Claude Opus in one step of our own reporting workflow, the step that needs judgement. Plain code does everything else.

UnderCurrent runs its own weekly, monthly and quarterly SEO and AI search reports as a scheduled workflow. Without it, someone would pull rankings and traffic by hand, then work out what changed and why. Now plain code pulls every number, including AI search visibility. Claude Opus only writes the analyst read, the part that says what the numbers mean and what to do next.

Each report is written without a person, and it fails loudly instead of sending an empty report. If Claude can't answer, the workflow falls back to a plain numbers summary. The August monthly report was written on 5 September with nobody touching it. Claude Opus runs only a few times a month per client here, so the extra cost is cents. A wrong read, though, could steer a whole month of work.

Try a lower effort setting first, because Anthropic says tuning effort is often a better lever than switching models. Effort is a setting that controls how many tokens Claude spends thinking and answering.

Opus 5.5 runs at medium effort by default and Sonnet 5.5 at high. Anthropic's effort guide says low effort brings "significant token savings with some capability reduction". Opus at medium might cost less than you'd expect. Sonnet at low might be all a simple job needs.

Two more levers cut the bill without changing models. The Batch API is 50% off for jobs that can wait, like overnight reports. Cache reads cost 10% or less of the input price, so a prompt you reuse all day gets cheap. Need your data routed through a set region? Anthropic's pricing page says providers such as Amazon Bedrock charge a 10% premium for regional endpoints.

Yes, and it's often the cheapest setup. The cheap model does the bulk work and the expensive one makes the hard calls. Anthropic calls this a multi-model strategy.

Its cost and intelligence guide describes two patterns. In one, a cheaper model runs the job and asks a stronger model when it hits a hard decision. In the other, a strong model plans the work and hands the bulk to cheaper workers. In one test, a strong coordinator with Sonnet workers cost 47% to 55% less than the strong model alone. It also scored 10 to 12 points lower.

For a small business, that might look like Sonnet sorting every email and Opus drafting replies to the rare complaint. It's the same idea behind most AI agents for business. Both models are also offered on Google Cloud and Bedrock, so the pattern works there too.

Choose Claude Sonnet 5.5 if your job repeats often and has a clear answer. Choose Claude Opus 5.5 if your job is rare, long or costly to get wrong.

Doing nothing has a price either way. Run Claude Opus on everything and every busy workflow pays double for answers Sonnet gets right. Run Sonnet on everything and the long, tricky jobs come back half right. Fixed, each job runs on the model that suits it.

UnderCurrent Automations builds workflows for small businesses across Australia on Claude, choosing the model step by step. If one job eats your week, get in touch and we'll map it into a workflow on the right model. The first chat costs nothing.

• How to use Claude in your business, a practical start for Australian owners.
• What is AI automation, how a workflow differs from a chat window.
• The simplest small business automation tasks, good first jobs for Sonnet.
• How much manual processes cost your business, the sum behind every workflow.
• What is business process automation, the bigger picture beyond one model.
• Top small business automation tools, where Claude fits among the tools.
• AI training for small business, helping staff pick the right model.
• n8n vs Zapier for small business, the platforms that run Claude workflows.