I think you're right for small clusters, you end up needing more sysadmins. But to manage 1000 node Kubernetes cluster, I suspect it can be done with less administration
Im managing 20000 vcpus infra both k8s and plain vms. IMHO there is no big difference there. It all depends on the tools you are using around orchestration.
In my experience having good sysadmins is still the key to best infrastructure management no matter the size of the company.
