I Did the Math on GPT-5.6. The $2.50 Terra Tier Is the One I'd Ship First.

Short summary

GPT-5.6 ships in three pricing tiers: Sol ($5/$30), Terra ($2.50/$15), and Luna ($1/$6) per million tokens. Terra is the practical default for most production workloads; Sol must save >$440/month in retries to justify its premium. Critical: prompts over 272K tokens trigger 2x input and 1.5x output pricing for the entire request, making naive cost estimates dangerously low.

• •Terra ($2.50/$15) balances cost and capability for general production; only move to Sol if concrete evals prove >$440/month savings versus Terra.
• •The 272K context boundary doubles pricing for the full request—a $300K prompt costs 95% more than simple token multiplication suggests.
• •GPT-5.6 shows higher agentic goal-drift than GPT-5.5; mitigate with granular permission boundaries (read, edit, external write, destructive, credential, purchase) rather than one approval bucket.

Generated with AI, which can make mistakes.