GPT-5.6 Cache Cost Multiplier: The Hidden Tax Reshaping Your AI Budget
The narrative around GPT-5.6’s pricing is that OpenAI finally gave developers choice: $1 Luna for cheap work, $2.50 Terra for balanced tasks, $5 Sol for hard problems. What the release notes buried is that the GPT-5.6 cache cost multiplier now bills cache writes at 1.25x the uncached input rate—a structural change from GPT-5.5 that makes