I would say no.
If you know what the weight of the item is, and you know the current market value is, then you know what its worth. A lot of places pray on someone not knowing what their item is worth. Example Pawn Shops and they cater to the I need money today to squeeze the person.
Example Gold. Get the current value per ounce. Then calculate the value per K. So 18k is 75% gold. 14k is .5833, etc.
Convert the ounce to grams=32. So lets say you have 10 grams of 14k jewelry. Lets use $1350 per ounce. Thats 42.18 per gram of 24k. Thats 24.60 per gram of 14k. x10 grams = 246.00 is the scrap. How close you can get to that 246 is the question where you have to know what you have. If the pieces are wearable and not damaged.. then that adds in your favor. Example single earrings, broken chains, loose teeth.. damaged stuff vs wearable.
Ebay sometimes works predictably well on scrap.. especially wearable.
Hope this helps.