An analogy that may resonate with readers here is that targeting zero fraud is like targeting 100% uptime in a computer system. You evaluate the business trade-offs and decide how many 9s of non-fraud are appropriate, knowing that (1) each additional 9 is more expensive than the last but only gives you 1/10 of the benefit, and therefore (2) infinity 9s (equivalent to zero fraud/100% uptime) is a useless aspiration for all practical purposes.