This is not true. On prem is extremely common for things like this because after ~6 months you'll have paid more in cloud costs than it would have cost to purch

This is not true. On prem is extremely common for things like this because after ~6 months you'll have paid more in cloud costs than it would have cost to purchase the GPUs. And you don't need to purchase new GPUs every 6 months. AWS would cost $50-100k/mo for something comparable.