codex-cost-estimate

Open-source Codex skill for producing realistic software rebuild estimates from an existing repository.

It inspects the repo, identifies product scope and technical complexity, estimates senior-engineer rebuild effort, and outputs a compact terminal-style summary with:

• Value per Codex Hour
• Speed vs. Human Developer
• Cost Comparison
• Grand Total Summary
• The Headline
• Assumptions

What It Does

• Sizes a repo by product area and code volume
• Accounts for architecture, integrations, and missing tests
• Estimates engineering-only, solo, startup, growth, and enterprise scenarios
• Uses git history heuristics to estimate Codex working sessions
• Produces a screenshot-friendly report inspired by public "AI ROI" posts, but framed more conservatively

Files

• SKILL.md: the installable skill
• cost-estimator.md: expanded reference prompt/spec for the same skill
• hybrid-build-cost-estimate.md: example output against a real project

Install

Copy SKILL.md into:

~/.codex/skills/codex-cost-estimate/SKILL.md

Or clone this repo and copy it from there.

Do not install cost-estimator.md directly unless you intentionally want the longer reference prompt instead of the packaged skill.

Usage

Use the skill when you want:

• a realistic rebuild-cost estimate for a completed codebase
• a tweet-style terminal report for a project
• a Codex ROI summary with explicit assumptions

Notes

• This repository is a Codex skill package, not a runnable application codebase.
• The ROI numbers are heuristics, not finance-grade accounting.
• The estimate is strongest as a decision-support tool, not as a formal quote.
• Missing tests, deployments, compliance, and maintenance can materially increase true cost.