You could make an analogy to getting a flu vaccine. There's a small up-front cost, but you're making a bet that it will prevent or reduce the severity of a larger issue down the road. There's no guarantee that the larger issue would ever occur, but "getting the vaccine" makes it less likely to occur, and less costly if it does occur. Skipping the "vaccine" is a reasonable choice if the business is willing to incur substantial damages in the case of a large event in the future. To put hard numbers to it, you could always show numbers like "X% of our customers are likely to leave if we leak all their data to hackers", and base it on documented examples from recent history.