First, let me start off by saying that I am generally not a seller. I like to collect, and therefore I usually only sell on eBay to get funds for something else.
But one thing has become clear to me. EBAY IS OFTEN LIKE A GIANT GARAGE SALE, and therefore many times really doesn't give a good indication of the real value of an item. And if you want to sell an item, it can be very risky leaving the final sale price up to open bidding. Look at what happened recently when a beautiful, authentic, PSA/DNA Wilt Chamberlain autographed basketball with a rare HOF 78 inscription was left to open bidding without reserve:
http://www.ebay.com/itm/SUPERB-NBA-WILT-CHAMBERLAIN-SIGNED-AUTOGRAP...
That amazing ball sold for only $367 !! Are you kidding me?! And it wasn't even an indoor/outdoor ball. It was an Official NBA Game Ball! That ball is worth anywhere from $1200 to $2000 and really closer to the latter than the former.
Oftentimes, the eBay market is a deflated market. There are just a lot of dealers looking for deals they can flip. They almost refuse to pay top dollar or just market value for an item. So if you leave your item up for open-bidding, you might just get screwed, like the seller of that awesome Wilt ball. SELLER BEWARE!
Pics below: