AI model APIs · head-to-head
GPT-5.6 Luna vs Grok 4.3
Same usage, official rates, ranked by nothing but price. Both rate cards, the monthly bill at five workloads, and the exact usage mix where the answer flips.
The pricing verdict GPT-5.6 Luna is cheaper while output tokens make up less than 7% of your total volume; past that, Grok 4.3 takes over. Most chat and agent workloads run 20–30% output.
Rate cards
| Per 1M tokens | GPT-5.6 Luna | Grok 4.3 |
|---|---|---|
| Input | $1 | $1.25 |
| Cached input | $0.10 | $0.20 |
| Output | $6 | $2.5 |
| Context window | 1M | 1M |
Monthly cost at five workloads
| Workload | Tokens / month | GPT-5.6 Luna | Grok 4.3 |
|---|---|---|---|
| Prototype | 1M in · 0.3M out | $2.80 | $2 |
| Small app | 10M in · 3M out | $28 | $20 |
| Production app | 50M in · 15M out | $140 | $100 |
| High volume | 200M in · 60M out | $560 | $400 |
| Heavy platform | 1B in · 300M out | $2,800 | $2,000 |
Exact switch point
Cost per 1M blended tokens is $1→$6 for GPT-5.6 Luna and $1.25→$2.5 for Grok 4.3 as your mix shifts from all-input to all-output. The lines cross at 6.7% output share — below it GPT-5.6 Luna wins, above it Grok 4.3 does. Long documents in, short answers out favours GPT-5.6 Luna; generation-heavy work favours Grok 4.3.
Standard on-demand rates from each provider's official pricing page, verified July 2026; figures exclude caching and batch discounts and any long-context surcharges. GPT-5.6 Luna: Batch API runs at 50% of these rates. Grok 4.3: Rates shown are for prompts under 200k tokens; above that, prices double. Price is one input — quality, latency and context limits differ. Confirm live pricing before committing.