Genuine question : why are hyperscalers like OpenAI and Oracle raising hundreds of billions ? Isn't their current infra enough ?

Naive napkin math : a GB200 NVL72 is 3M$, can serve ~7000 concurrent users of gpt4o (rumored to be 1400B A200B), and ChatGPT has ~10M concurrent peak users. That's only ~4B$ of infra.

Are they trying to brute-force AGI with larger models, knowing that gpt4.5 failed at this, and deepseek & qwen3 proved small MoE can reach frontier performance ? Or is my math 2 orders of magnitude off ?