How did Matilda come to know the real cost of the necklace?

Answer – After the loss of necklace Matilda give another diamond necklace and they got in high debt. After 10 Long years they pay all the debt. One day Mrs. Forestier meet Matilda and then Matilda told him the truth about the necklace. Then Mrs. Forestier said that the necklace was not more than 500 francs. This time she knows the real cost of the necklace.