Pawn shops have two ways of going about it. You can sell an item to the pawn shop or you can use it as collateral for a loan.
Brandi pawned her wedding ring for $20. She could have gotten the ring back for that $20 plus $16 in fees. I'm quite sure she intended to never go back, though. I imagine she could have gotten more for the ring. I paid $360-ish for hers. I don't know what the guy at the pawn shop would have appraised it for, but the maximum she could have gotten would probably be less than half the value they say it is at the pawn shop.
When I went to the pawn shop (different shop but same idea), I mentioned that Caity's ring was worth approximately $4500 when I got it and the guy told me that they try to sell jewelry for about half of what it would cost new at the jewelry store. They also have to make a profit. So I'd have gotten less than half the value of the ring. I'd have sold it to the shop instead of using it as collateral for a loan. So I'd have probably gotten less than $2000 for it... probably a lot less. One thing to remember, too, is that they value it at what they think they can sell it for... and people looking at pawn shops for jewelry are probably (in general) the kind of people who can't tell the difference between an iffy-quality diamond and a top-quality diamond.
Whereas since the store I got it from worked with me, I got a good bit more than that in a check, plus I have the store credit for whatever jewelry I may need later.
Ebay might be your best course of action... you might be better off with craigslist. Set a fair price for it and if you're willing to wait a few days, everyone will win because you'd get more than the pawn shop would give you and the buyer would pay less.