What is the cost of a container?
That tianon/dockerfiles/Dockerfile is from 2 years ago, at a time when you actually had to run a container, to use it as data volume container.
But since docker 1.8, you don't need to run a data volume container anymore.
You can just docker create it.
More recently, you docker volume create it: no image needed. No cost in process or bandwidth for a DVC.
So there is no cost in term of process anymore for a data volume container.