The AI price war is on: GPT-6.1 Sol and Sonnet 5.5 land one day apart at the same $2/$10 price

#What happened

One day apart, OpenAI and Anthropic each cut the price of near-flagship AI by roughly 80%. On September 29, at DevDay 2026 in San Francisco, OpenAI released GPT-6.1 Sol, which it says delivers "near-Astra intelligence" at a fifth of GPT-6 Astra's standard token prices. Sol is priced at $2 per million input tokens and $10 per million output tokens, with cached input at $0.10 per million — 95% below the standard input rate. The day before, on September 28, Anthropic shipped Claude Sonnet 5.5 at the exact same headline price, $2 and $10 per million tokens, unchanged from Sonnet 5 — but says it runs more than 30% faster and costs up to 30% less per completed task because it burns fewer tokens and makes fewer tool calls to finish the same work.

The numbers behind the pitch: on DeepSWE v1.1 (coding benchmark), GPT-6.1 Sol scores 75% versus Astra's roughly 74.8% — essentially a tie — while OpenAI says it cuts cost per task by about 80%. On OSWorld 2.0 (computer-use benchmark), Sol comes within 2.1 percentage points of Astra's 73.5% flagship score while costing around $1.30 per completed task against Astra's $9.30, per benchmark data reported by Vellum AI. Anthropic reports Sonnet 5.5 scoring 70.6% on Terminal-Bench 4.0, ahead of its own Opus 5.5 flagship at 66.4% and far past the previous Sonnet 5's 10.3%. On GDPval-AA v2.1, a knowledge-work evaluation, Sonnet 5.5 scored 1,844 — just two points behind Opus 5.5's 1,846.

The caveats: on harder problems the gap widens. On Terminal-Bench Science, Sol scores 57% at $5.47 per task while Astra hits 68.1% for $23.80. Sol also arrived just one week after GPT-6 Sol (which itself scored 68.8% on DeepSWE), so most of Sol's coding gains came from that prior release. Underneath both launches sits open-weight pressure: Alibaba's Qwen3.8-27B runs as low as $0.0427 per million input tokens on OpenRouter and scores 34 on the Artificial Analysis Intelligence Index — well below both Sol and Sonnet 5.5 on capability, but cheap enough for high-volume, low-complexity pipelines.

Availability: Sol is live for Plus, Pro, Business, Enterprise, and Edu users in ChatGPT and Codex, and developers can call it through the API as gpt-6.1-sol starting September 29. An Ultrafast variant, running up to eight times faster in Codex, is coming in the following days.

#Why it matters

Two labs, one week, the identical pitch: don't pay flagship prices to get flagship-adjacent results. When GPU capacity gets cheaper faster than demand grows, every lab races to own the price point where actual production traffic lives. For teams shipping code or running browser agents, the cheap tier is now the rational default; the flagship only earns its premium on frontier reasoning work.

Verified Sep 30, 2026.