Bava Metzia 104B

אהני כתיבה לגירעון.

The Talmud answers: The writing of this statement in the document is effective for depreciation. If the collateral depreciates in value, the creditor may claim the remainder of the debt from the debtor’s property.

רבי יוסי היה דורש לשון הדיוט. דתניא, רבי יוסי אומר: מקום שנהגו לעשות כתובה מלוה ⁠– גובה מלוה. לכפול ⁠– גובה מחצה.

§ The Talmud continues: R' Yosei would also expound common language, as it is taught in a baraita that R' Yosei says: In a location where they were accustomed to formulate the terms of a marriage contract as one would formulate the terms of a loan, i.e., the precise value of her dowry is written in the marriage contract, then upon the termination of the marriage due to divorce or the husband’s death, the wife collects the sum of her dowry as a creditor would collect payment of a loan. In other words, she receives the entire sum recorded as her dowry. Conversely, in a place where the custom is to double the written sum of the dowry in the marriage contract to honor the bride, so that it should appear as though her father is providing her husband with a considerable dowry, she collects only half of the sum written in the marriage contract.

נהרבלאי גבו תילתא, מרימר מגבי נמי שבחא.

The Talmud relates: The rabbis of Neharbela collected, i.e., allowed the wife to collect, 1/3rd of the stated sum, as the custom in their location was to write 3 times the actual amount of the dowry in the marriage contract. Mareimar would allow the wife to collect even the added value of those sums that the father of the bride had written in the marriage contract in honor of his daughter.