OpenAI returns fire against Anthropic's Opus 5.5 with better, cheaper GPT-6 models

Published Sep 22, 2026, 3:01 PM EDT Simon is a Computer Science BSc graduate who has been writing about technology since 2014, and using Windows machines since 3.1. After working for an indie game studio and acting as the family's go-to technician for all computer issues, he found his passion for writing and decided to use his skill set to write about all things tech. Since beginning his writing career, he has written for many different publications such as WorldStart, Listverse, and MakeTechEasier. However, after finding his home at MakeUseOf in February 2019, he would eventually move on to its sister site, XDA, to bring the latest and greatest in Windows, Linux, and DIY electronics. Sign in to your XDA account Summary OpenAI launches GPT‑6 Sol and Luna, touting big cost‑intelligence gains. Sol and Luna cost 50% less than GPT‑5.6 promo pricing, thanks to caching and inference wins. Pricing: Sol $2/1M in, $10/1M out; Luna $0.10/1M in, $0.50/1M out. Phew; I did say the world of AI moves quickly, didn't I? We're still getting over Anthropic announcing Claude Opus 5.5, which promises Fable 5.1 performance at 40% cheaper cost. Now, OpenAI has retaliated with an announcement of it's own, with GPT-6 Sol and Luna OpenAI reveals GPT-6 Sol and Luna They're a lot cheaper than their older models As announced on the OpenAI blog, the company has revealed the Sol and Luna versions of GPT-6, the model it recently released. The big win for power users here is a sharp decrease in cost: The GPT‑6 models lead across the cost–intelligence curve, combining exceptional capabilities at every tier with infrastructure that delivers them efficiently at scale. Improvements in caching and inference let us serve these models at lower cost, and we’re passing those savings directly on to users and customers by reducing API prices for Sol and Luna by 50% compared with their GPT‑5.6 promotional pricing. This discount for Sol comes to $2 for 1 million input tokens and $10 for 1 million output tokens, down from 5.6 Sol's $4 and $20 respectively. Similarly, GPT-6 Luna is down to $0.10 and $0.50, from GPT-5.6's $0.20 and $1.20.