I agree with what you mention, but it is not only creating the gpt, it is marketing, social networks, paid advertising to publicize the chat bot, this is not only creating it with gpt builider, because otherwise the caht bot will be lost in the store in millions of gpt.
Here is something that as a gpts creator, I am the one who uses my own custom chatbots, usually I do not look for another, except for dalle, which I still use under the paid subscription.
In short, we are in a revolution and as long as the API is closed, the business will be in the API, buying tokens to sell tokens.