How much is the rarest dog worth?

I'm curious, what is the value of the rarest dog in the world? Is it measured in monetary terms or is there some other form of valuation that applies? And how does one even determine what makes a dog the rarest? Is it based on breed, lineage, or some other unique characteristic? I'm eager to learn more about this fascinating topic and understand the factors that contribute to the value of such a rare creature.