I am much like Swanky;as I also prefer to have one or two important pieces of jewelry a year. I do know that certain names such as Tiffany, Harry Winston,etc. are likely to bring higher prices should you need to auction them.
It is certainly better than thinking of clothes as an "investment" Maybe if you are buying Princess Diana's,or Marilyn Monroes?
I love my jewelry,but I know it would not bring in the retail cost,if I had to sell it? Unless I was famous or infamous;which I'm not and hope not. I can say that it is a good investment for me(I didn't have to pay for it) and a poor investment,based only on monetary appreciation for my husband. LOL