It’s all about the last few seconds.
I have been trying to buy a Canon L-Series f2.8 16-35mm wide-angle lens. The going price used is somewhere between $950 and $1,050. I have set a top bid at around $1,000 three times, and in the last three to seven seconds, someone comes in just above. It can’t be much above, because you can "buy it now" for $1,100 to $1,200. And those lenses don’t move.
Fascinating. The one that just closed went from $885 to $1,050 in the last five seconds.