Can someone validate I have this correct: I can use chatGPT through the browser (chat.openai.com) for free, but to use any of these clients, I need a paid subscription (after the initial $18 thing runs out).

Hmm... duh. Of course I just asked chatGPT this and got this reply, for anyone else wondering:

"Yes, you are correct that you can use ChatGPT through the browser for free by accessing the OpenAI GPT-3 Playground at chat.openai.com. However, if you want to use the API to integrate ChatGPT into your own software or application, you will need to sign up for a paid subscription after the initial $18 promotional credit runs out."