[vintagewhitesox]

There is a binding contract between the buyer and seller. the fact that an event happend "after" the contract was entered into does not change the terms. Buyer has to pay. If he backs out, I would sue him for the amount he agreed upon.
But I practice criminal defense and not this stuff so what do I know?

Here's another question.
What if the role was reversed? What if Brady had announced his retirement the next day? The value of the ball would increase. Should the buyer have to then pay more to the auction house?