That was the first time it happened in baseball. It's happened in hockey twice, Toronto in the 1942 Stanley Cup final against Detroit and the New York Islanders in a 1975 second-round series against Pittsburgh.
Players usually do it to vent their frustration. A lot of the times they are having a bad game and take it out on the umpire.
Sometimes managers actually want to get kicked out of the game. It motivates the team and gets the crowd into the game.
I don't know why you wouldn't want to put it on ebay. That is by far the best place to sell it. You have the capability of making it a 1 day auction if you want. Plus you get a much broader audience than with Craig's List which is more local.