The invoice and the measurement are the same document
You are billed a share of what was measured. If nothing was saved, there is nothing to bill — and that is a structural property, not a promise.
Most infrastructure spend is a forecast that someone defends for a year. You buy capacity against a projection, and the projection is the thing your finance team is asked to believe.
This is the other shape. The engine measures what your traffic cost and what it cost after; you pay a share of the difference. The document that bills you is the document that measured you, so there is nothing to reconcile between them and no separate set of books where the saving lives.
It also means the incentive points the right way. We do not earn more by selling you more capacity, and we do not earn anything at all in a month where nothing was saved.
A CFO can check the arithmetic without trusting us, because the arithmetic is the measurement.