The cost of ledgers and their auditing is not a meaningful proportion of retail interest rates in the current environment, which is dominated by the cost of fun

The cost of ledgers and their auditing is not a meaningful proportion of retail interest rates in the current environment, which is dominated by the cost of funds, default risk, marketing/customer acquisition costs and profit. Reducing or eliminating that cost should not make the costs of lending change in any noticeable way, because you're reducing something that is insignificantly small anyway.