Codex Cost: Pay-per-Use API vs a ChatGPT Subscription Plan

Melvin Vivas · X post · 2026-05-04 · Open on X

Topics: AI Dev Tools & Productivity, LLMOps, Deployment & Monitoring · Level: beginner

Summary

The creator ran OpenAI's Codex coding agent on pay-per-use OpenAI API billing for about 2 hours and found it very expensive. He says a subscription plan is much better value for long agentic coding sessions.

Key points

• Running Codex on per-token OpenAI API billing got very expensive after about 2 hours of work.
• For heavy agentic coding, a flat-rate subscription plan is better value than API billing.
• Agent loops use many tokens, so watch costs before running long sessions on API keys.
• The creator says not to repeat the experiment; he only did it out of curiosity.

Resources mentioned

• OpenAI Codex · tool · openai.com · paid
  OpenAI's coding agent. In the diagram it writes code, fixes review findings and drives the build loop. The creator also used it to make this video.
  Also in: An agent bot that installs and drives Codex on its own (Melvin Vivas on X · notes), Asking a Coder bot to install Codex (Melvin Vivas on X · notes), Sign in with ChatGPT: Setting Usage Limits for Each App (Melvin Vivas on X · notes), Codex Cloud Environments Must Be Saved & Published Before Use (Melvin Vivas on X · notes) and 240 more
• OpenAI · tool · x.com · free
  An AI model provider whose models can be used through managed connectors.
  Also in: Creator's favorite OpenAI DevDay announcements (Melvin Vivas on X · notes), OpenAI Agents API with Bring Your Own Sandbox as a backend for a 'software factory' (Melvin Vivas on X · notes), Building Software Factories on the OpenAI Agents API (Codex-Powered) (Melvin Vivas on X · notes), Coworker: Free Local-First Desktop App for Running AI Agents (Melvin Vivas on X · notes) and 11 more

Try this

• Use a subscription plan instead of pay-per-use API billing for long Codex sessions.
• Don't run Codex for hours on API billing without watching costs.