It sounds like you are working in either 14k or 18k solid gold, the price of which is not going to come down again for a long time, if ever! Due to this fact, my advice is to adjust the prices of your entire previous inventory to reflect at least a 50% to 75% portion of the difference, because you will never be able to replace your materials stock and continue to pay yourself if you do not. By increasing at just a portion, you will satisfy both the need to be able to keep your customers as well as personally survive. When pricing your new pieces use your 'real time' cost and explain what you are doing to your customers, as they question the difference in prices between pieces that are side-by-side. It is my opinion (due to a recent experience with a similar situation) that your customers will appreciate your honesty and you will probably sell your older pieces more quickly!
Answer contributed by Dale "Cougar" Armstrong