Function rebuild_cost 

pub fn rebuild_cost(depth: u32, inflated: u64, external_base: bool) -> u64

What it cost to produce an object, as the cache scores it.

depth + 1 inflates and depth delta applications over inflated bytes. Deliberately a coarse integer and not a timing: a duration measured on the reader’s thread carries that thread’s scheduling, and two identical objects would then score differently depending on how busy the box was.