No docker is not virtualisation, the poster below is talking about docker for desktop which is a nice gui wrapper around it in a VM, but by definition docke itself does not use any form of virtualisation. If you had a modern Linux server you can install any of the container runtimes, e.g. docker, podman to run containers or something like K3S which is effectively a lightweight kubernetes if you wanted to run a lot of different containers and have a central way of managing them

No, it’s a 56% increase. The increase is based on the before number, not after. 8->16 would be a 100% price increase