It's really interesting watching who bids on who - the auctions on Sky Channel 809. There is some serious cricketers in that room - Ponting, Kallis, Fleming, Vettori, Sehwag etc...
There is a lot of tactical bidding which can drive up random players prices and also various types of players can be worth inflated prices e.g.. Indian keepers. This due to no one wants to use an overseas in that position so they become a very sort after player.
Also recent form and IPL history can make a player e.g. Bravo and Pollard because the owners have happy memories of them. And recent eye catching form obviously helps.
I think Root didn't get sold because he was up early doors and all the teams wanted to wait and see what happens etc... he has a good chance of being brought back.