While overall supply also plays a role in the price, the fact may be that more people are keeping the Pokemon Center version of Destined Rivals ETBs sealed rather than opening them
As long as a creature you control has the granted ability when you draw your third card in a turn, that ability will trigger
Its been exploding over the last few years
The card is quite powerful as it not only allows a player to summon one monster more than the one they can summon each turn but it also allows them to summon one from the opponent's graveyard
(2010-06-15) If you cast a spell with rebound from anywhere other than your hand (such as from your graveyard due to Sins of the Past, from your library due to cascade, or from your opponent's hand due to Sen Triplets), rebound won't have any effect
Perhaps even more impressive is Uria's ability to be unaffected by all other traps, and destroy the opponent's traps as necessary