# Which AI coding model should you pick for your budget?

Date: 2026-10-28 · Author: Robert Scales · https://guidetoartificialintelligence.com/en/learn/pick-coding-model-by-budget/

**Answer:** At $0, start with Codex on ChatGPT Free, Gemini 3.8 Flash's free API tier or a local open model; at $20 a month, Claude Pro with Claude Code or ChatGPT Plus with Codex covers most solo work. Pay per token through an API only when you need automation, and default to mid-priced models such as Claude Sonnet 5.5 or GPT-6.1 Sol.

AI coding costs come in two shapes. A **subscription** charges a fixed monthly price and limits how much you can use. An **API**, the programming interface developers call directly, charges for every **token**, a small piece of text about three-quarters of a word, that the model reads or writes. Subscriptions are easier to budget; APIs are easier to automate. Most learners should start with the first.

The tiers below use prices as of October 2026.

## The budget ladder

| Monthly budget | Good choice | What you get | Watch out for |
|---|---|---|---|
| $0 | Codex on ChatGPT Free | The light GPT-6 Luna model in the ChatGPT desktop app, subject to rollout | Small model, so keep tasks small |
| $0 | Gemini 3.8 Flash, free API tier | A capable model for scripts and experiments | Free-tier content may be used to improve Google's products |
| $0 | A local open model | Qwen3.8-27B or Muse Glimmer on your own machine | Needs about 24 GB of graphics memory |
| $8 | ChatGPT Go | Codex with Luna for light coding | Desktop app only, light tasks |
| $20 | Claude Pro ($17 if paid yearly) | Claude Code with Opus, Sonnet and Haiku | No free Claude Code tier below it |
| $20 | ChatGPT Plus | Codex in the CLI, editor, web and iOS, with GPT-6.1 Sol and Luna, plus cloud code review | Usage varies with model and task |
| $100 and up | Claude Max (5x or 20x Pro usage) or ChatGPT Pro ($100, $200 or $500) | Much higher limits for daily heavy use | Upgrade only after you keep hitting limits |

For most people learning to build with a coding agent, one $20 plan is the sweet spot. Pick the company whose chat app you already use, since the same subscription covers both.

## Pay-per-token prices

If you build your own tools, run agents in CI, or need more than a plan allows, you pay per million tokens:

| Model | Input | Output | Typical use |
|---|---|---|---|
| Claude Haiku 5.5 (prompts up to 100K tokens) | $0.10 | $0.50 | Helper and bulk jobs |
| GPT-6 Luna | $0.10 | $0.50 | Bulk, well-defined tasks |
| Gemini 3.8 Flash (until Dec. 31) | $0.75 | $3.75 | Everyday coding on a budget |
| Claude Sonnet 5.5 | $2 | $10 | Default for real coding |
| GPT-6.1 Sol | $2 | $10 | Default for real coding |
| Gemini 4 Argon (until Nov. 30) | $2 | $10 | Doubles to $4 / $20 on Dec. 1 |
| Claude Opus 5.5 | $4 | $20 | Hard, long tasks |

Notice how the market has lined up: Sonnet 5.5 and GPT-6.1 Sol cost exactly the same, and so do Haiku 5.5 and Luna. That makes choosing by quality on your own tasks easier, since price no longer decides it.

## A worked example

Say you run 40 agent tasks a month. Each reads 1 million tokens, 900,000 of them cached project context, and writes 30,000 tokens. Using each company's cache-read price (Sonnet 5.5 and GPT-6.1 Sol $0.10, Opus 5.5 $0.20 per million):

- **Sonnet 5.5 or GPT-6.1 Sol:** 0.1 × $2 + 0.9 × $0.10 + 0.03 × $10 = $0.59 a task, about **$24 a month**.
- **Opus 5.5:** 0.1 × $4 + 0.9 × $0.20 + 0.03 × $20 = $1.18 a task, about **$47 a month**.

These figures are illustrative and leave out cache-write fees. Compared with a $20 plan, the API is not cheaper for this amount of work; it is simply more flexible.

> **Try it:** Count how many coding tasks you gave an agent last week, multiply by four, and run the calculation above for your top two models. If the result is near or above $20, a subscription is probably the better deal.

## How do you keep a monthly coding bill predictable?

**Prefer a fixed price.** A subscription caps your spend by design. When you reach a limit, both companies let you continue for extra money: Anthropic through usage credits at API rates, OpenAI through ChatGPT credits. Decide in advance whether you will turn those on, rather than in the middle of a task.

**Check your usage as you go.** In Codex, the `/status` command shows your remaining limits in the CLI; in Claude, the usage page in settings shows where you stand. On Claude's plans and on ChatGPT Plus, usage is counted over five-hour windows, with weekly limits possible on top, so pacing your work across the week helps.

**Use the mid-tier model by default.** Start every task on Sonnet 5.5, GPT-6.1 Sol or a similar model, and move to Opus 5.5 or GPT-6 Astra only when a task fails twice. On Codex's Plus plan, OpenAI estimates roughly 5 to 45 messages per five hours with Astra against 15 to 160 with GPT-6.1 Sol, so the flagship can drain your allowance quickly.

**On the API, use the discounts.** Keep instructions and project context identical at the start of each request so they are billed at the cached rate, and send work that can wait through batch processing, which costs half price at both Anthropic and Google.

**Mark price changes on your calendar.** Gemini 4 Argon's API price doubles on December 1, 2026, and Gemini 3.8 Flash's rises on January 1, 2027. Introductory prices are a good time to experiment, not a basis for a long-term budget.

**Set a cap you can live with.** If your API account lets you set a monthly spending limit, set one before you connect an agent to it. An agent that loops on a failing test can burn through tokens overnight; a cap turns that surprise into a pause.

## Sources

- Codex pricing: https://developers.openai.com/codex/pricing
- Pricing | Claude: https://claude.com/pricing
- Gemini Developer API pricing: https://ai.google.dev/gemini-api/docs/pricing