While I am no fan of Ebay as a whole, my understanding is that they have an option for a seller to list an item with a 'buy it now' price. If I read your post correctly, you had such a price listed, and a buyer wanted to pay it. If all that it is correct, then I think a refusal to accept the buy it now offer (barring good cause-which does not seem to exist) would be the questionable course of action (basic offer and acceptance). I think you did what was right, and what your principle wanted. If the others had wanted to bid, they should have got on to doing so, hazard of waiting till there are 2 seconds left to make your move.

As for ethics violations, I can only say....what the $%^&*&^%%.