The answer you gave to your own question is right, they are a collectors item. When you say you are getting into PM , really you are referring to bullion. Some bullion does go for a dollar or two more an ounce than others but it's still one ounce of silver.
The Dragons are numismatic, modern numismatics created by the mints. If you get the right one, you can do really well, check the thread here that talks about the mongolia wolverine, owl and hedgehog series.
Sometimes there is bullion that crosses into numismatics for example the Canadian wildlife Timberwolve coins that were issued at about the same price as a maple but now sell for 10 to 15 dollars more per coin.
There are a lot of variations on these, such as graded coins, error coins, and the traditional numismatics such as the U.S.A. 1909-s V.D.B. cent . You are on the right track though with your comparison to art.