James is exactly right!

It may still be your property but when you put a chip up for auction, you have agreed to sell it to the highest bidder at what ever the final price is, unless there is a reserve.

Also, ending the auction early and selling to an outside buyer is against Ebay's UA. You could jeopardize your standing with ebay and not be able to sell there anymore.

As a seller of a chip, don't you think that you are kind of shooting yourself in the foot as your chip may not realize the full sales price that it might of at auction? I think so in a lot of cases.

So, if you are not willing to let an auction run it's course don't put it up for auction, simple as that!

Cheers!
Bill