OpenAI and Anthropic Slash LLM Prices 80%

OpenAI slashed GPT-5.6 Luna's input price by 80% to $0.20 on July 30, 2026, a shock in the LLM market. Just weeks later, Anthropic made its temporary Sonnet 5 price cut permanent on August 10, 2026, keeping the model at $2 per input token. OpenAI followed by dropping GPT-5.6 Sol's input price by 20% to $4 on September 22, 2026. On that day it also cut GPT-6 Sol's input price to $2, halving the cost of the popular model. Meanwhile, Anthropic released Claude Opus 5.5 on September 22, 2026, pricing it at $4 per input and cutting cache reads by 40-60%. The cumulative effect is a 75% reduction in total cost for models like GPT-6.1 Sol. GPT-6.1 Sol matches Astra's performance while keeping cache read costs minimal. At $0.20 per input, GPT-5.6 Luna is now cheaper than any open-weight model, reshaping the LLM pricing war.