During the game, bombing your way into the wrong caves results in you losing rupees as the old man inside makes you pay for the "door repair charge". These become a lot more frequent in the second quest.
One of the hint ladies, if you pay her the maximum amount of rupees, merely says, "Boy, you're rich!"
Old men found in labyrinths avert Friendly Fireproof, taking damage from your weapons and even retaliating with plasma balls from their nearby fires. Whaling on them can be rather therapeutic if you're frustrated from their cryptic hints, although they cannot be killed.