There is a number that does not appear in any standard bank or fintech reporting that I would argue is the most commercially significant number the business generates. I want to describe how to calculate it because once you can see it, it is very difficult to look away from.
Take the number of customers acquired in a given period. Take the revenue per customer per month from a cohort that did reach full commercial productivity. The difference between what the fully productive cohort produced and what the actual acquired cohort produced, measured against the acquisition cost of both, is the financial cost of the retention gap.
In financial services businesses at growth stage, that number is consistently larger than any budget line associated with retention investment. The business is spending substantially more on acquiring customers it cannot keep than on keeping customers it already has. That is a financial governance position that deserves a number on it.
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