Laptops/desktops are cheaper per flop than any datacenter hardware by a good order of magnitude.

The problem is that expectations rise in datacenters, hardware/power/security/availability guarantees cost real money. Then the operator providing these guarantees expects some margin.

You can see this most clearly with "developer desktops", a gcp instance costs about 10x a hetzner instance which costs between 5 and 10x the same hardware sitting in the back of an office somewhere. While all of these premiums matter for 24/7 systems under active development, they don't really matter for ephemeral small scale workloads.