OK I've spent all morning reading about this. I think that when you say "work", you're talking about the work of doing DOM updates. Rendering a VDOM is still considered cheap.
It's akin to doing `Header( LoginLink( GetLoginName() ) )` versus
``` Header(); check_for_interrupt(); LoginLink(); check_for_interrupt(); ... ```
The interrupt between rendering components (pieces of work) can now cancel the whole render operation (because say, the parent component has now been updated / wants to be re-rendered), or can pause the render tree while something like a high-priority animation frame is rendered.