GPT-6 Astra vs Sol vs Luna: Which Tier Should You Use?

GPT-6 comes in three pricing tiers — and the most expensive one costs 100× as much per token as the cheapest. Picking the wrong tier means overpaying per token — the spread is exactly 100× from Luna ($0.10) to Astra ($10.00) per 1M input tokens. Here's how the tiers compare and a practical framework for choosing.

The pricing, side by side

Prices verified September 26, 2026 — always confirm on the official pricing page before deciding.

What each tier is for

Luna — the cheapest tier ($0.10/$0.50 per 1M). Built for high-volume, well-scoped tasks: classification, extraction, translation, first-draft summarization, FAQ bots — for tasks where you've verified quality on your own evals, it's 95% cheaper per token than Sol.

Sol — the middle tier on price (20× Luna, 5× below Astra per token), for agentic workflows, code generation. Which workloads justify the premium is a quality question for your own evals.

Astra — the highest-priced tier (5× Sol on every published rate: $10.00 vs $2.00 input). Whether the premium is worth it can't be answered from prices alone.

A decision framework

1. Start with Luna. Prototype on the cheapest tier. If quality meets your bar, you're done — and 95% cheaper than Sol.
2. Measure the quality gap. Run the same eval set on Luna and Sol. If Luna passes, ship Luna. If it fails on reasoning-heavy cases, those specific cases go to Sol.
3. Reserve Astra for high-stakes calls. Even teams that need Astra rarely need it for every request — route only the critical subset there.
4. Revisit quarterly. Models improve and prices move.

Worked example: 1M requests/month

Say each request uses 1,500 input tokens and 400 output tokens — 1.5B input + 0.4B output tokens per month:

• All Luna: 1,500 × $0.10 + 400 × $0.50 = $350/mo
• All Sol: 1,500 × $2.00 + 400 × $10.00 = $7,000/mo
• All Astra: 1,500 × $10.00 + 400 × $50.00 = $35,000/mo
• Hybrid (80% Luna / 20% Sol): $1,680/mo — 76% cheaper than all-Sol

The hybrid pattern in the example above costs $1,680/mo — 76% less than all-Sol: cheap tier for the bulk, strong tier where it matters.

The bottom line

Don't default to the middle tier out of habit. Benchmark Luna first, route selectively, and reserve Astra for what truly needs it. For most workloads, the right answer is a mix — and the savings are concrete: the hybrid example saves $5,320/mo vs all-Sol. Want more tactics? See our 10 ways to cut your GPT-6 bill.