Well, some of us have morals!
I just sold my old moped on eBay and bidding started at £230, or Buy It Now at £280 (which someone has!)
I got four offers by email during the two days it was up there. A couple of people offered £250. I just replied and said it was against mine, and eBay's policy to end the auction early for an outside offer. The other two offers were stupid - £230, and one for £200. I had to go into another room to get the belly-laughs out of my system in case I felt the urge to reply. ;-)
Some people just don't think twice about these kinds of things though. Even my own mother said, "why don't you get someone to bid on it for you to up the price?"
I couldn't believe I'd been raised by her when she said that. :-o