Here people of a city are spoken of as if they were the sons of the city. These words could refer to 1) only the young men of Jerusalem or 2) all the people of Jerusalem. (See: [[rc://en/ta/man/jit/figs-metaphor]])
The author speaks of the precious sons of Zion as if they were considered to be inexpensive clay jars. Alternate translation: "people think of them as worthless, like the clay jars that potters make" (See: [[rc://en/ta/man/jit/figs-metaphor]])