worth one’s weight in gold

“Mr d'Urberville says you must be a good girl if you are at all as you appear; he knows you must be worth your weight in gold. He is very much interested in ' ee --- truth to tell.” “德伯维尔先生说，如果他没看错的话，你一定是个好姑娘;还说你千金难买呐。说实话，他对你非常中意。”（第六章）