1. Diamond necklaces are very meaningful and private things, so people are reluctant to buy old ones and wear them directly as decoration. Therefore, buyers only have jewelry recycling agencies, and there is no market, so there is no price;

2. Jewelry recycling institutions aim at making profits. He grasped the characteristics of monopolizing the market, so he tried his best to reduce the price.

3. After the diamond necklace is recycled, it only needs to be re-melted, purified and reprocessed, so the process is complicated and the reprocessing cost is high;

The diamond necklace will be worn for a long time, so it will depreciate.