The seller does not see the bids that never took effect (i.e., the high bid beyond the selling price)

It can jump fast if two of the bidders are like me: I set the price I am willing to pay, place the bid at that amount, and never monitor it. I don't have the time to go back and re-bid every time it goes up a dollar or ten. If an item is worth $600 to me, that's my bid. If someone else is doing the same, bidding can escalate from $1 to $500 or $600 in a flash.