The example of dramatic irony is:
A wife cuts and sells her hair to buy a watch chain for her husband, who has sold his watch to buy combs for her hair.
In this scenario, the audience knows that both the wife and husband have made sacrifices for each other without knowing about the other's actions, which creates a poignant contrast between their intentions and the outcome. This situation highlights the irony of their love but also of their misunderstanding, which characterizes dramatic irony.