Like class and society, the issue of wealth weighs heavily (hah! Pun-tastic) on the characters of A Little Princess. Sara finds herself going from a rich heiress with plenty of fine clothes and exquisite dolls to a penniless little girl dressed in rags. But she never loses her identity. Even in poverty, she's still the same Sara who is curious about the world and loves to make up stories in her head. She keeps her fine manners, curious spirit, and brave soul. But we're still glad she gets her fortune back at the end.
When Sara's father dies, she has to deal with both her newfound monetary poverty as well as the poverty of being without family and love.
Characters like Miss Minchin look at others through how much money they have, but they don't take into account the wealth of personality and skills that people have.