OpenAI cuts token prices in half for new GPT-6 Sol and Luna models

OpenAI released GPT-6 Sol and GPT-6 Luna on September 22, 2026, about 90 minutes after Anthropic shipped Opus 5.5. Sol costs $2 per million input tokens and $10 per million output—half Opus 5.5’s $4/$20 and level with Claude Sonnet 5. Luna costs $0.10 and $0.50. OpenAI said more efficient caching and inference produced 50% lower API prices than GPT-5.6 promotional rates; Sol is 50% cheaper than GPT-5.6 Sol both ways, and Luna is 50% cheaper on input and 58.3% on output. Anthropic says Opus 5.5 is 20% cheaper per token than Opus 5 and about 40% cheaper on typical workloads. CONTESTED: OpenAI says Sol makes about half as many mistakes as its predecessor on its internal factuality test, “approaching Astra-level reliability at much lower cost.” Those scores come from OpenAI alone, without independent reproduction at launch, and it is open whether its Anthropic comparisons included same-day Opus 5.5. Outside benchmarks versus Opus 5.5 and the full ChatGPT rollout were still ahead. Claude Fable 5.1 remains $10/$50. Gemini 3.8 Flash stays $0.75/$3.75 through Dec. 31, 2026, then $1.50/$7.50 on Jan. 1, 2027.