It takes a very trained eye to be able to value gold, silver and diamonds. First off, if it's jewelry, you need to be sure that its intrinsic value isn't worth more than what it would be in scraps. For example, a gold Cartier bracelet may be worth more as a bracelet than it would be if you just melted the gold down and sold it off as scrap gold. The reason for this is because the brand, Cartier, gives it more value, and some gold buyers use this knowledge to give their customers a better deal on their items.
The reason that most people sell gold in NYC is that they need the money, plain and simple. This is why it's important to do the proper research in order to find a buyer that can offer you a fair payout, but that's not all, you need to be sure that they're trust worthy. It's usually a good idea to check up on a company on yelp, citysearch, as well as other credible places online where others share their experiences dealing with certain businesses.
Also, the price of gold can make your offer fluctuate for the better or worse, so if you're a frequent seller, then be sure to be able to check up on the price changes daily in order to maximize the offers that you receive from the buyers. When you find a good buyer, stick with them! Don't try to fix something that isn't broken, because gold selling in NYC can be quite the hassle.
Thank you for taking the time to read my post, and if you're interested in selling your gold in NYC, I highly recommend Global Gold & Silver, and you can check them out at their website: http://globalgoldandsilver.com/