It is reasonable for a king to request gold, silver, and jewelry because in China, the groom is expected to present a betrothal gift to the bride's family when getting married. This is a traditional custom in Chinese culture aimed at expressing the groom's respect and gratitude towards the bride's family, and also represents the groom's family's recognition and acceptance of the bride. The content and value of the betrothal gift vary depending on factors such as regional differences, cultural customs, and social and economic conditions. Generally, a betrothal gift from the groom's family includes cash, gold and silver jewelry, clothing, household goods, food, tea, etc. The quantity and quality of the gifts often depend on the relationship between the two families and the groom's family's economic strength.
It is important to note that the betrothal gift should not be viewed as an exchange of goods or a way of purchasing a marriage. Instead, it should be seen as a symbolic expression of the groom's respect and gratitude towards the bride and her family, and to demonstrate the groom's sincerity and goodwill.