As antique jewelry is really based on the collectability and style of an item, it is difficult for people to appreciate the craft involved in handmade work, as they only see the Gold value or Diamond value fluctuate over the years.
If Gold goes up or an object gets older, the value may or may not increase. Antiques and collectables are a subjective thing. Supply and demand plays an important part in the way we invest. Good quality will always be good quality but just because something is old does not make it worth a lot of money. A hundred year old bucket is still an old bucket unless it has historical significance.