CoreWeave owns and runs their own infra, they aren't a middleman.

There are middlemen that can actually get you better prices and availability than you can get yourself, because they buy or rent in volume, and can pit the hyper scalers against each other to get better prices.

If you want even a handful of A100s on GCP you need to buy reserved instances, but lots of resellers will rent them to you hourly, and they have RIs underneath.