What you’ll get from this lesson: Learn to distinguish course fees, subscriptions, usage-based charges, and equipment costs, and write down your own starting budget.
Prerequisites: No software installation required. Prepare a work example that can be shared publicly or has had sensitive information removed.
Before building an Agent, I start by separating the costs. Course fees, the monthly fee for an AI account, the cost of calling a model from a program, and equipment and operating costs often get lumped together. Once you understand the differences, you’re less likely to buy a subscription only to discover that another way of accessing the service is billed separately.
Start by Separating Four Types of Costs
The first is course fees. This website’s plan is to make L0 available to read without logging in, and L1 available for free hands-on practice after logging in. Later paid content is subject to the plans described on the website. Free learning materials do not mean that all the AI tools you use are free.
The second is an AI subscription. As of this review’s reference date, September 11, 2026, OpenAI lists the ChatGPT Plus web subscription at US$20 per month. Applicable taxes and the final checkout amount still depend on what is shown in your account. The product benefits included in a subscription have usage limits, so you cannot convert the monthly fee directly into a guaranteed number of conversations.[1]
The third is API usage or other usage add-ons. ChatGPT subscriptions and the OpenAI API are billed separately, so first check which access method your tool currently uses. If you are not using the API, there is no need to set up API billing just for this conceptual lesson.[1][2]
The fourth is equipment and operation. Using your existing computer may mean you do not need to buy another machine. However, electricity, internet access, maintenance time, and any hosting you may need later are still costs. Running a model locally does not make the entire system free to operate.
Estimate Your Starting Costs with an Example That States Its Assumptions
Suppose you keep using your current computer, choose ChatGPT Plus at US$20 per month, and use only the usage supported within that plan, without purchasing API usage, extra credits, or hosting. In this example, the additional fixed AI subscription cost is US$20 per month, while API and new equipment expenses are provisionally set to zero. Record electricity, internet access, and applicable taxes separately.
This is only an example of how to separate costs, not a guarantee that your Agent will cost only this amount each month. In particular, the Pi sign-in method and model access route specified by the course still need to be checked against the published course-material version and tested with the actual account. You cannot infer that all third-party integrations have the same authorization simply because Codex supports subscription-based sign-in.[2]
Measure Usage Once Before Estimating a Month
Choose one small, representative task. Record which models or paid tools you actually used, the total cost, and how many times you expect to run it each day. Use “cost per task × tasks per day × days per month” as your first estimate, then note the differences caused by retries, multi-turn conversations, and long documents.
This is a budgeting exercise, not a provider’s billing formula. Different tasks consume different amounts, and one message should not be treated as one model call. Before using a service, check which limits you can configure. If it offers only alerts rather than a hard cap, write manual stopping conditions into your budget card.
Don’t Buy a Powerful Machine at the First Stage
What I most wanted to emphasize in the original recording was to check whether the model can do your work before buying hardware. Testing a small task that contains no sensitive information makes it easier to see what you actually need than buying expensive equipment at the outset.
Fill in all four cost categories and mark which ones increase with usage before deciding whether to move on to L1. You do not need to buy every service in advance.
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Sources Checked
[1] OpenAI, “What is ChatGPT Plus?” Checked on 2026-09-11.
[2] OpenAI, “Authentication.” Checked on 2026-09-11. For full URLs and details on where this guidance does not apply, see “Source Verification and Re-recording Revisions” in this package.