Why the karat changes the price so much
Karat tells you how much of the metal is gold. 24K is pure, 18K is 75% gold, 14K is 58.5% and 10K is 41.7%. The rest is copper, silver, zinc or nickel, which add strength and color but almost no value.
So a gram of 14K is worth a little more than half a gram of pure gold. That’s why a heavy 10K chain can be worth less than a light 18K ring.
Price per gram is not what you’ll be paid
The numbers above are melt values. Every buyer keeps a margin for testing, refining and risk. Pawn shops usually pay 35–60% of melt, local jewelers 55–75%, and mail-in refiners that publish their prices pay around 90%.
Knowing the per-gram melt value before you walk into a shop is the easiest way to spot a lowball offer.