MATH PUZZLE: Can you replace...

One day a man went to an auction. While there, he bid on a parrot. He really wanted this bird, so he got caught up in the bidding. He kept on bidding, but kept getting outbid, so he bid higher and higher and higher. Finally, after he bid way more than he intended, he won the bid - the parrot was his at last!
As he was paying for the parrot, he said to the auctioneer, "I sure hope this parrot can talk. I would hate to have paid this much for it, only to find out that he can't talk!"
"Don't worry," said the auctioneer, "He can talk. Who do you think kept bidding against you?"