Are you still short of gift inspiration (giftspiration)? Are they notoriously hard to please? Perhaps you want to show them precisely how much you love them in cold, hard, monetary terms? Maybe they're making your life needlessly difficult by stubbornly not revealing what they want? Maybe they're testing you? Maybe this year they should just choose for their ruddy selves?
Whatever your reasons, take the sensible option and give them the gift that gives them the gift of giving themselves a gift.