You've often heard that 'buying jewelry is a good investment'? Ever try to sell it? Why did that decent item not present well to the buyer?
Well, it is simply this:
1) Your purchase was on a much higher market level than should have been for resale;
2) Your selling market is lower than your purchase market;
3) You were not as careful in your product as you thought;
4) You are a buyer of junk or common jewelry; or,
5) The world shifted on you in time and surroundings.

Assuming that time and surroundings are a constant, one can make a return plus profit buying jewelry. We do it everyday and make a living at it.
The key is simple . . . carefully consider the level of the purchase, the level of the sale, and the buyer, the seller and the product. Inquiries welcomed.