Ask HN: The Cost of Building an AI Workflow with Open-Source Tools for a Startup

I'm planning to build an AI workflow using open-source tools like models, vector databases, and frameworks (e.g., crewAI, langchain, llamaindex) without doing any training or fine-tuning. Can anyone share the average computational cost to go from an idea to a finished product using cloud-based services? I'm specifically interested in the average total cost for developing "multi-agent AI workflow using chain-of-thought".

Thanks.