Empathy to figure out the opposition's tension level and possible place/assess Aspects like "Pushing His Credit Line" or "I'll Have to Sell the Kids". Deceit to defend against that kind of read by bluffing (it's kind of funny how those skills flip flop in this situation). Resources to make "attacks". Intimidation or Presence could maneuver well too, like "Aura of Menace" or "Don't Even THINK About Bidding".
Although I'm not sure you'd be attacking the other bidders. Maybe it's a series of "attacks" against the item's stress track? I'm not sure. Perhaps make the bidding into a zone map, where it's a sort of track from "observer" up to "final bid", and each zone has increasingly higher border ratings. You'd use Resources to move instead of Athletics and you could make Resources blocks on the zones add to the border rating perhaps. Yeah, I like this concept better than "attacking" the item or the other bidders (although you certainly could attack them subtly and socially to take them out).
Hell, if you've got a friend set up they could be making Scholarship rolls to hack your opponents' bank accounts or something.
