I agree with
@drbgt40, your analysis doesn't account for real life circumstances. I used to get called in on weekends when our walk in fridge or freezer would fail. We spent plenty on good gear and maintenance, but failures happened regardless.
More important than cost of fridge failure with cost of discarded food, is the risk of being sued or fined due to food poisoning or even death of customers - peace of mind in that regard is worth paying for, not just for health and safety of customers, but also for risk to brand image from adverse publicity of food poisoning.