Ask HN: Are companies building models or leveraging existing ones to add AI?

How are companies going about adding AI-powered functionality into their products today?

As we all know well, there are countless new products and features emerging across various domains that utilize AI. For instance, today I came across a SaaS product that uses AI to streamline scheduling interviews. Are these products developing their own AI models, or are they building on top of OpenAI or similar platforms? Perhaps they are using a combination of both approaches? If they do rely on OpenAI or another paid service, are the economics sustainable with the current pricing models? I’m looking to understand the best practices for integrating AI into an existing product or developing a new AI-powered product in today's landscape.