Most gold marketers give you half the market value for the weight of gold. And if you go up to them with a stone set that isnt a ruby, sapphire, diamond , or emerald, They will take a big pliers and crush the stones off the finding and the weigh the gold and do a Sp Gravity to etermine carat weight. remember 24 carat is 100% gold, 18 carat is 75% and 14 karat is 48% by weight of gold. You can figure out the carat weight yourself by making a graph of these three points. So, lets say you have an 18 carat ring and it weighs 1 oz, and gold is at 1000$ an ounce.
18 k = 0.75% Au.
You will get 375 $ for that rings gold from a gold marketer.
Its not a great deal working with these guys. I had several old class rings that were all busted up and I took em in to get em appraised fopr sale by a gold marketer. After all the calculations and deductions, I took em to getmelted down and had gold "nugget" chains made for my wife and daughter. They were cool and looked just like the drawings I made for the jeweler who was good at making free form gold chochkies.
I think that, if you can do better than the 50% market max , youre doing pretty ok.