It's interesting to see all these companies building products wholly off of OpenAI's platform. What happens if OpenAI changes their mind about pricing or access some day? Isn't this an existential risk to all "AI" companies that don't actually do the AI part?

This is one of many, many open LLM models that are approaching GPT level now. They're not on the same level yet, but given the rate of progress in this field, it's safe to say that OpenAI's moat will not be there forever.

Also, their level is already sufficient for A LOT of tasks that people use OpenAI's APIs now.