if its a nice offer, take it... or give the guy who asked a somewhat ridiculous amount and see what he has to say... it has happened all the time to auctions I have been bidding on, and i have done it one time also...
if you think you can get a better deal, then pull it and sell it
eBay is business, and a bunch of people will be disappointed at first, but wont hold it against you.. but better pull it before a lot more people bid on it... if its only one guy that has a bid, and you get an offer of $300, contact the bidder and explain the situation, if he says he is not willing to pay that much, pull it
IMHO
Dave