Auction participants are bidding across all available seats to upgrade. Because of this, Seatfrog has pre-determined price points (Milestones) within the auction, where upgrades are awarded to the highest bidder to reach (or pass) that price. This can be a bonus to participants who put their best price forward straight away, and also allows for more seats to be upgraded.
Usually, an auction is only for a single item. Price point upgrades enable us to sell multiple upgrades within a single auction. By putting your best price forward, you could be upgraded instantly and end up with a great deal!
For example: James is travelling from Kings Cross to Edinburgh and the current price in his auction is £19, but James bids £25. An instant upgrade price could be at £24 and James wins an upgrade instantly for less than his highest bid. The auction will continue and the next bid will need to be £26 or over.