Rent an AI’s Brain!? Your Guide to API Usage and Pricing

📝 3 Things You’ll Learn in This Article

1️⃣
What is an API?
You’ll understand what this “translator” that connects AI to your service really is.
2️⃣
How do you use it?
No programming required! You’ll find out what you need to do in just 3 simple steps.
3️⃣
How much does it cost?
The burning question: the cost of renting an AI. You’ll learn how the pricing works and get a rough estimate.

Chapter 1: So, What is an API Anyway? 🤔

Are you thinking, “I know generative AI is amazing, but it probably has nothing to do with my job”? What if you could call upon that “amazing AI brain” as easily as you use an app on your phone? The thing that makes this possible is an “API”.

At first, I also thought it sounded complicated, but it’s really not! It’s just like the setup of a “restaurant”. Click on the characters in the diagram below, and a tab will open showing their specific roles.

Role: The Customer

You are the customer who comes to the restaurant, looks at the menu, and decides what to eat. All you have to do is tell the waiter, “I’d like the carbonara.” You don’t need to know how the pasta is made or what equipment is in the kitchen.
It’s the same in the world of APIs. You just need to decide on your “request,” like “I want you to write this text” or “I want you to generate this image.”

Role: The Waiter

This is the efficient waiter who takes the order from you (the customer) and relays it to the kitchen (the AI). It has two important jobs.
First, it must accurately translate your request (“I want carbonara”) into a language the kitchen understands (“One order of Pasta #5!”). Second, it must bring the finished dish from the kitchen right to your table. It’s because of this waiter that you can communicate smoothly with the kitchen.

Role: The Chef (Kitchen)

This is the super-chef in the kitchen who receives the order from the waiter (API) and creates the perfect dish (the final output). The kitchen is hidden from the customers’ view. Inside, there’s state-of-the-art cooking equipment and secret recipes (the AI’s complex inner workings), but you don’t need to know about any of that.
You just have to enjoy the delicious meal (the text or image generated by the AI) that the waiter brings to you.

Chapter 2: How Do I Use It?

“Okay, I get that the API acts as a translator. But how do I actually use it?” I hear you. Don’t worry! You don’t need to do any programming yourself. The most important thing is simply knowing “how to make a good request to your engineer.” Tap the steps below to see the flow.

1

Sign Up & Get Your “Secret Phrase”

First, your company signs a contract with an AI provider like Google or OpenAI. Then, you’ll receive a special secret phrase called an “API Key” to use their service. Usually, a department like IT will manage this key.

2

Make a “Request” to an Engineer

Next, it’s your turn! You tell an engineer “what you want the AI to do.” For example, “When I press this button, I want it to create 5 different versions of a product description.” The more specific, the better!

3

Have it Integrated into the System

Based on your “request,” the engineer will write a program that connects the system to the AI using the API. Once this is done, you’ll be able to use the AI with the click of a button!

Chapter 3: What About the Cost? 💰

When you’re renting an AI, the price is obviously a big concern. Most generative AI API pricing is based on a “pay-as-you-go“ model. In other words, you only pay for what you use. It’s a lot like your cell phone data plan.

The unit used to measure “what you use” is the “token.” You can think of it roughly as “the amount of text or data being processed.”

💡 Quick Tip: What’s a Token?

A token isn’t always one character. AI models break text down into chunks. For English, one word is often one token, but longer words might be more. The key takeaway is that the length and complexity of your text directly impacts the token count, and therefore, the cost.

Simple Price Simulator

What if you asked an AI to write a short article (approx. 3000 tokens)?

Number of Tokens: 3000 Tokens

For a high-performance model (like GPT-4o)…

~ $0.02

※This is a rough estimate for the input (your request) cost only. The output (the AI’s response) is billed separately.

Major Service Pricing (for reference)

※This is reference information as of June 2025, showing the price in USD per 1 million tokens. Please always check the official websites for the latest pricing.

Model Name	Input Price	Output Price
GPT-4o (OpenAI)	~ $5.00	~ $15.00
Gemini 1.5 Pro (Google)	~ $3.50	~ $10.50
Claude 3 Sonnet (Anthropic)	~ $3.00	~ $15.00

Many services offer a free monthly tier with a certain amount of usage, so you can try them out easily!

Conclusion: You Can Already Rent an AI’s Brain!

With APIs, AI is no longer a technology of the distant future. It can become a reliable partner that helps you with your work right now. Why not start by thinking, “Which part of my job would I like to ask an AI to handle?”