In the last few years I have bought 4 tractors, Combine, disk, dump wagon, header trailer, equipment semi trailer & a few other items on Auction time. 

 Some items were a "deal" some items were not a "deal".

 I have heard "rumor" the sellers can see your max bid.   I know Auction time does not like "shill bidding", but  if someone not closely attached to the seller bids for the seller how are they to know?   I know on the combine My max bid was $9000 over what I paid.  The disk was  about $4000.    But I guess some/most sellers are honest.   The $100 a time last minute bidders are just "playing" IMO.