Three escalating numbers are enough to teach moral behavior

In Singapore, we should pay fine when behaving inappropriately in subway: S$500 when eating or drinking, S$1000 when smoking, and S$5000 when using flammable goods. Interestingly, eating durians is also inappropriate but the fine amount of doing so is not clarified. I suspect that Singapore government seems to know intuitively that people follow rules if they see a set of three escalating numbers.