> Another interesting thing is that you pay for 100% of a VM virtual CPU even if it is only utilised 40%, but the cloud is selling your other 60% capacity to another user

AWS don't overprovision CPUs outside of the t instance range, in which you get vCPU credits, not full vCPUs. If you rent an apartment but don't use it, is it the landlord's fault you don't? The landlord can't rent the same appartement to another client.

Especially on AWS/GCP/Azure, where there are many alternatives ( Lambda, Google Cloud Run, Google App Engine, etc.) where you pay per compute used.