Something may be of great personal value, but on its own is just worth what other things like it are worth. Receiving a letter in the mail from a special friend could be worth its weight in gold because gold is a precious metal; it costs a lot of money to buy an ounce of it. The figure of speech means something has great value to you.
非常有價值的
一件事情對某人來說特別有價值但就其本身而言也許只是同等價值.好比說收到一位特別的朋友寄來的信件可能會讓你覺得他像黃金一樣有價值。