GPT-5.6 vs GPT-5.5: Pricing, Tiers & Whether to Upgrade
Published 2026-06-27 · 6 min read
OpenAI shipped GPT-5.6 just two months after GPT-5.5, and the headline change isn't only capability — it's the lineup. GPT-5.5 was a single flagship; GPT-5.6 splits into three tiers: Sol, Terra and Luna. Here's how GPT-5.6 compares to GPT-5.5 on price, and which one is actually cheaper for your workload.
How the tiers map
- GPT-5.6 Sol → the GPT-5.5 successor. Same $5 / $30 per 1M as GPT-5.5, but the stronger model (OpenAI positions Sol ahead of Claude Fable 5 on TerminalBench). Upgrading costs nothing extra.
- GPT-5.6 Terra → the value play. $2.50 / $15 — literally half of GPT-5.5 — for OpenAI's "daily driver" tier aimed at high-volume business work.
- GPT-5.6 Luna → a brand-new budget frontier. $1 / $6, with no direct GPT-5.5 equivalent. The cheapest frontier-class OpenAI model yet.
GPT-5.6 vs GPT-5.5: price table
| Model | Input /1M | Output /1M | Cached | Tier |
|---|---|---|---|---|
| GPT-5.5 | $5.00 | $30.00 | $0.50 | Previous flagship |
| GPT-5.6 Sol | $5.00 | $30.00 | $0.50 | New flagship |
| GPT-5.6 Terra | $2.50 | $15.00 | $0.25 | Daily driver |
| GPT-5.6 Luna | $1.00 | $6.00 | $0.10 | Budget frontier |
Should you upgrade from GPT-5.5?
- Want the best model? Move to Sol. It's the same price as GPT-5.5, so it's a pure capability gain.
- Want to cut cost? Drop to Terra and halve your bill — if your workload doesn't truly need the flagship. Most production traffic doesn't.
- High volume and cost-sensitive? Luna at $1 / $6 is the cheapest way to stay on a frontier-class model.
On an 1,800-in / 400-out workload at 200,000 calls/mo, GPT-5.5 and Sol both run ~$4,200/mo, Terra ~$2,100/mo, and Luna ~$840/mo. Run your real numbers in the calculator.
How GPT-5.6 compares to Claude and Gemini
Price only matters relative to the alternatives. Per 1M tokens:
| Model | Input /1M | Output /1M |
|---|---|---|
| GPT-5.6 Sol | $5.00 | $30.00 |
| Claude Fable 5 | $10.00 | $50.00 |
| Claude Opus 4.8 | $5.00 | $25.00 |
| Gemini 2.5 Pro | $1.25 | $10.00 |
| GPT-5.6 Luna | $1.00 | $6.00 |
GPT-5.6 Sol sits below Claude Fable 5 on price and matches Claude Opus 4.8 on input. At the low end, Luna is cheaper than Gemini 2.5 Pro on both input and a typical blended call. See the full price comparison, or the cheapest LLM API guide.
Bottom line
GPT-5.6 isn't a price hike — it's more choice. Sol upgrades GPT-5.5 for free, Terra halves the cost for everyday work, and Luna is the new budget-frontier option. Full breakdown in GPT-5.6 pricing, or compare every model on the live table.