OpenAI: GPT-5.6 Terra vs SpaceXAI: Grok 4.5

For a sample job of 1 million input tokens and 250,000 output tokens, Grok 4.5 costs $3.50 and GPT-5.6 Terra costs $5.00, so Grok 4.5 is about 1.4 times cheaper for the same work.

GPT-5.6 Terra reads up to 1,050,000 tokens at once, roughly 1,575 pages of text, against about 750 pages for Grok 4.5.

On our blended benchmark score GPT-5.6 Terra leads 71.1 to 65.0.

Across the 18 tasks where they differ, GPT-5.6 Terra scores higher on 11 (Code Review, Code Refactoring, Bug Fixing and others), Grok 4.5 on 7 (Code Completion, Code Documentation, Regex Writing and others).

Pick GPT-5.6 Terra if you need long documents or benchmark performance; pick Grok 4.5 if you need lower cost.

Costs use current list prices per million tokens; page counts assume about 0.75 words per token and 500 words per page.