You may have a right to end your auction early, but as per eBay policy:
Reasons for ending listings early include:
-The item is no longer available for sale.
-There was an error in the starting price or reserve amount.
-There was an error in the listing.
-The item was lost or broken.
When there are 12 hours or fewer remaining and the item has a winning bid, including a reserve met bid, sellers may not make any changes to the listing, including ending the item early. Sellers may cancel bids, but not end the item.
Note: Sellers are not permitted to cancel bids and end listings early in order to avoid selling an item that did not meet the desired sale price. This is considered to be reserve fee circumvention.
I'm sure the seller can twist the situation around enough to squeeze it through eBay's rules, but everyone knows that's not usually the case.
Unfortunately you see this more and more on eBay, especially with custom cues. I'd rather bid on an item with a reserve than one that includes "Item for sale locally..." I doubt you have to include this phrase to give yourself the option of ending it early, but as soon as I read it I know that's what will happen if the seller's "unlisted" reserve isn't being met.
My personal opinion is that if an item is up for auction, it shouldn't be available for purchase anywhere else. Imagine a live auction in progress, bids being placed, and suddenly the auctioneer stops and says "Sorry, this item is no longer available. The owner just sold it to someone in the parking lot." I doubt this happens very frequently, and my guess is because it isn't allowed.
I fully appreciate not wanting to sell your $2000 cue for $600, but that's why a reserve price can be set. I know "everyone" does it, but it's pretty cheesy IMO.