Mainly any gold Jewelry or something made of gold or gold coins value is determined by the factors Purity, Weight and current price of gold.
We get less amount than for what we bought them because of the weight. Jewelry's weight always decreases as it had used. There are also some buyers who generally try to cheat.
So if you want to sell your old ornaments, I suggest you to First check the purity of your gold then know the weight and at the last know the current price of gold. After confirming these three factors go to sell your gold.