it's because this argument of "what is $0.01 more?" can be extended forever, implying you are willing to pay an infinite amount of money for anything. since we know this is silly, we try to understand what our "real" maximum is. this is difficult to do for exactly the reasons you mention in your comment! surely $0.01 is negligible! there is a tension here.

and so, absolute max price is not a fantasy - the world would be absurd if it were - but instead its a real and difficult to construct value

It can be extended forever in theory, and sure, that is an interesting philosophical discussion, but it isn't in practice. We're discussing sniping. That means you make the choice once: do I send in a last-second bid that's $.01 more than my "max price", or do I not?