http://revach.net/article.php?id=1755

Section: Halacha   Category: Tshuvos
Rav Chaim Kanievsky - Rare Stamps And Rare Opportunity
You own two rare stamps that are worth a great fortune.  Your friend comes and rips one of the stamps deeming it worthless.  However because of this the price of the first stamp increases to the point that it more than makes up for the damage done by ripping the first stamp.  Is your friend Patur from paying because you have no net damage?

Rav Chaim Kanievsky says that he is probably responsible to pay for the damage he caused to the stamp he ripped.  The fact that your other stamp increased its value because of this is irrelevant.

Disclaimer: We try to convey the Tshuva to the best of our ability. We admit that our understanding may not be accurate. Please also understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.