We have not set a price yet.
We would rather say that plainly than publish a number we would have to walk back.
When we do set one, it will be worked out from the infrastructure a host stops paying for, not from what WordPress hosting happens to charge. That is a figure we can measure, and the measurements are already public.
The short version of what they say: a plugin-free site serves a page from about 12 MB of memory, against roughly 1.9 GB of stack a tuned WordPress needs to answer the same page on the same machine. For a host running many mostly-idle sites that is a different machine bill rather than a smaller one. The Technology page has the method, and the places where WordPress is still ahead of us.
Want a figure for your own fleet?
Tell us how many sites you run, which plugins are on them, and where you host them today. We will come back with what it would cost and what it would save, against your numbers rather than a table.