GPT-5 vs Grok 4
GPT-5 is cheaper for every workload modelled here.
List prices checked
Specifications and rates
| Property | GPT-5 | Grok 4 |
|---|---|---|
| Input per 1M | $1.25 | $3.00 |
| Output per 1M | $10.00 | $15.00 |
| Cached input per 1M | $0.125 | $0.750 |
| Blended (3:1) | $3.44 | $6.00 |
| Context window | 400K | 256K |
| Max output | 128K | 64K |
| Inputs accepted | text, image | text, image |
Source: OpenAI pricing (May 2026) · xAI pricing (May 2026). Published list prices only — committed-use discounts, regional variation, and per-request charges are not included. Not yet independently re-checked against the vendor’s page.
Monthly cost by workload
Identical token volumes through both rate cards. Output-heavy profiles are where the ranking flips.
| Workload | GPT-5 | Grok 4 | Cheaper |
|---|---|---|---|
| In-app chat assistantA support or help assistant handling a few thousand conversations a month, with short prompts and short answers. | $75 | $135 | GPT-5saves $60/mo (44%) |
| RAG over documentsRetrieval-augmented answering where each request stuffs several retrieved passages into the prompt, so input dominates. | $525 | $1,125 | GPT-5saves $600/mo (53%) |
| Coding agentAn agentic loop that reads files and writes patches, generating heavy output and re-sending large context on every turn. | $1,500 | $2,700 | GPT-5saves $1,200/mo (44%) |
What each one is for
GPT-5
by OpenAI
OpenAI's flagship, priced aggressively below the other frontier models on input and with a 90% cached-input discount that makes long system prompts nearly free to reuse.
Grok 4
by xAI
xAI's flagship, priced to match Claude Sonnet exactly, with a large context window and live access to posts on X as a differentiator.
Common questions
- Is GPT-5 or Grok 4 cheaper in 2026?
- GPT-5, for every workload modelled here. On a blended 3:1 basis it costs $3.44 per million tokens against Grok 4's $6.00.
- Which has the larger context window?
- GPT-5, at 400K tokens against 256K. A larger window only helps if you can afford to fill it — the cost of one full-context request is in the table above.
- Which is cheaper for output-heavy work like agents?
- GPT-5, at $10.00 per million output tokens against $15.00. Reasoning tokens bill as output, so for agentic loops this axis usually decides the invoice regardless of what the input rates look like.
- What is not included in these figures?
- Batch-processing discounts, fine-tuning, long-context surcharges above a provider's standard tier, and any enterprise agreement. These are published pay-as-you-go list prices, checked against each provider's own pricing page on the date shown.
- Is switching from Grok 4 to GPT-5 worth it?
- On price alone it is about 43% cheaper on a blended basis. Whether that survives contact with your workload depends on output quality and on retry rate — a cheaper model that needs two attempts is not cheaper. Model the specific volumes in the calculator before you migrate.