Simulating realistic Agentic workflow parameters (40,000 in / 1,500 out with 65% cache reuse). GPT-5.3 Codex delivers a 2% cost reduction over Gemini 3.1 Pro.
| Traffic Volume Tier | GPT-5.3 Codex Monthly | Gemini 3.1 Pro Monthly | Monthly Savings by picking GPT-5.3 Codex |
|---|---|---|---|
| 1,000 reqs/mo (Dev/Testing) | $50.05 | $51.20 | Save $1.15 / mo |
| 10,000 reqs/mo (Small App) | $500.50 | $512.00 | Save $11.50 / mo |
| 100,000 reqs/mo (Growth Production) | $5,005.00 | $5,120.00 | Save $115.00 / mo |
| 1,000,000 reqs/mo (Scale SaaS) | $50,050.00 | $51,200.00 | Save $1,150.00 / mo |
GPT-5.3 Codex is 2% cheaper for Agentic workflow workloads. At standard Agentic workflow parameter ratios (40,000 input tokens, 1,500 output tokens, 65% cache hit), GPT-5.3 Codex costs $0.0501 per request compared to $0.0512 on Gemini 3.1 Pro.
GPT-5.3 Codex offers a context window of 256,000 tokens (max output: 64,000), while Gemini 3.1 Pro offers 2,000,000 tokens (max output: 128,000).
At 100,000 requests per month, using GPT-5.3 Codex saves $115.00 every month (or $1,380.00 annually) compared to Gemini 3.1 Pro.
Prompt caching is the single biggest lever — each step re-reads prior context. Summarize or prune tool outputs before appending them to the transcript. Cap the step budget; runaway loops are the #1 surprise on agent invoices.