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Claude Sonnet 5.5 vs GPT-6.1 Sol: API Cost Comparison

The two default mid-tier models most teams shortlist for production chat, RAG and tool use. Their list prices are identical, so caching and output length decide the bill.

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Claude Sonnet 5.5 and GPT-6.1 Sol pricing side by side
Side by sideClaude Sonnet 5.5
Anthropic
GPT-6.1 Sol
OpenAI
Input / 1M$2$2
Output / 1M$10$10
Cached input / 1M$0.10$0.10
Batch discount50% off50% off
Context window1M tokens1.05M tokens
Long-prompt surchargeNoneAbove 272K input
TierMid-tierMid-tier

Workload

tok
tok
%

Repeated system prompt or docs

%

Jobs that can wait hours

Models

Anthropic
OpenAI
Google
Mistral
DeepSeek

$ per 1M tokens, input / output

Monthly cost · 30 days

Cheapest
$2,100
Claude Sonnet 5.5
Priciest
$2,100
GPT-6.1 Sol
Spread
1.0×
priciest vs cheapest
Per 1K users / mo
Claude Sonnet 5.5
$2,100$1,050
GPT-6.1 Sol
$2,100$1,050
Per 1K users assumesrequests per user per day.

Where the money is

Caching half your input on GPT-6.1 Sol (a shared system prompt or document) would cut about $570/month.

You're looking at ~$2,100/month.

Most AI products I audit can cut that 30–60% with routing, caching and shorter prompts.

Get a cost-cutting audit
01

Cost at three traffic levels

Same request on both: 2,000 input tokens and 300 output tokens, no caching, no batch, 30-day month.

Monthly cost of Claude Sonnet 5.5 vs GPT-6.1 Sol
Requests / dayClaude Sonnet 5.5GPT-6.1 SolDifference
1,000$210$210$0
10,000$2,100$2,100$0
100,000$21,000$21,000$0

By request type:

Cost per 1,000 calls by request type, Claude Sonnet 5.5 vs GPT-6.1 Sol
Per 1K callsClaude Sonnet 5.5GPT-6.1 Sol
Classification or routing call$0.9000$0.9000
Support chat reply$5.50$5.50
RAG answer over your docs$16.00$16.00
Long document summary$90.00$90.00
02

When to pick which

  • Input tokens cost the same on both ($2 per 1M).
  • Output tokens cost the same on both ($10 per 1M).
  • Cache reads cost the same on both ($0.10 per 1M).
  • Both offer 50% off for batch processing.
  • GPT-6.1 Sol has the larger context window (1.05M tokens vs 1M tokens).
  • GPT-6.1 Sol bills the whole request at a higher rate once input passes 272,000 tokens.

Claude Sonnet 5.5: The default for production chat, RAG and coding assistants: strong quality at a mid-tier price.

GPT-6.1 Sol: General-purpose production workloads: chat, tools and RAG at a mid-tier price with cheap cache reads.

03

Verdict

It's a wash on price

On list price they are a wash for a typical request. Decide on quality for your task, latency, and which caching model fits your prompts. Then run both on 50 of your real prompts and compare answers and billed tokens side by side.

04

How the math works

Every provider bills input tokens (your prompt, system prompt and retrieved documents) and output tokens (the reply) separately, per million. Output is usually 4–5× the input price, so chatty apps are output-heavy and RAG apps are input-heavy.

cost per request = (fresh_in × input_price
+ cached_in × cached_price
+ out × output_price) / 1,000,000
× (1 − batched_share × batch_discount)
monthly = cost per request × requests per day × 30

Two adjustments are applied automatically. Introductory prices (currently on some Gemini models) are used until their end date. Long-prompt surcharges kick in when your average input crosses the provider's threshold: 272K tokens on current OpenAI models, 100K on Claude Haiku 5.5.

Not modelled: cache-write premiums, priority or fast tiers, regional surcharges, image and audio tokens, and reasoning tokens a model spends before answering (they bill as output, so add them to your output estimate if you use extended thinking).

05

Questions

Which is cheaper, Claude Sonnet 5.5 or GPT-6.1 Sol?
For a typical request of 2,000 input and 300 output tokens they cost about the same: $0.00700 on Claude Sonnet 5.5 and $0.00700 on GPT-6.1 Sol. Caching and output length decide which is cheaper for your workload.
Can I use both Claude Sonnet 5.5 and GPT-6.1 Sol?
Yes, and many teams do. Put a thin routing layer in front of both: send the requests that need the stronger or larger-context model to it, and everything else to the cheaper one. Keep prompts provider-neutral so you can move traffic when prices change.
How often do Anthropic and OpenAI change prices?
Often enough that a comparison older than a few months is suspect. The prices on this page were verified on 7 Nov 2026 from each provider's own documentation, linked in the Sources section.
06

Sources

All prices are list prices from each provider's own documentation, standard tier, in USD, last verified on 7 Nov 2026. Providers change prices often; if a number here disagrees with the source, the source wins.

07

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Fine print

Tools: on the house.
Engineer: by the hour.

Knowing your AI bill was free. Cutting it in half isn't, but I'm cheaper than the overspend.

I'm Himanshu, an AI and full-stack engineer. I build MVPs, AI agents and the growth plumbing around them for early-stage startups.

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