To be able to answer this question, it is important to trace the plot of the story to the point of the dialog. The short story "The Monkey's Paw" by W. W. Jacobs begins on a stormy night as Mr. White and his son are playing chess, with Mrs. White knitting nearby. A visitor, Sergeant-Major Morris, arrives. He has just returned from a long sojourn in India and has brought back a dried-up monkey's paw that he claims is magical. He says that a holy man put a spell on it so that three men can each have three wishes. He has already used his wishes, and they were granted, but he does not seem pleased about it. The last wish of the man who had the paw before him was for death. Impulsively he throws it in the fire, but Mr. White pulls it out.
Morris tells Mr. White how to wish for things but advises him not to do it. After Morris leaves, the family talks about what to wish for, and eventually Mr. White holds up the paw and wishes for 200 pounds. The next morning they make fun of the wish. Their son, Herbert, goes off to work. At dinnertime, a well-dressed stranger comes to their home. He appears ill at ease.
Now we come to the dialog in the question. The stranger comes from the company where their son works. He informs Mr. and Mrs. White that there has been an accident on the job and that their son was caught in the machinery and was killed. He says that the company does not claim responsibility, but "in consideration of your son's services," the company wants to offer them a payment of 200 pounds.
It is immediately obvious at this point that the monkey's paw has granted Mr. White's wish for 200 pounds, but not in the way that Mr. and Mrs. White expected. Instead of a blessing, the money is a curse because it comes at such a terrible price. The visitor is uncomfortable in telling them that their son has died, even though he is bringing them a gift of 200 pounds. Mrs. White is the first to understand the implication of what the visitor is telling them, and she takes steps to reassure her husband by putting her hand on his in sympathy.