If the the cards in a box are worth more than the sealed box, you can bet that people will be opening boxes like crazy, which in turn increases the supply of the cards in the set and brings down the prices of the cards
Building a Pokemon card collection from the ground up involves that you focus on quantity before hunting down specialty holographic Charizards or first edition old cards
Meanwhile, I could not help but wonder about the perfect storm that created Gardevoir/Gallade: no suitable Psychic Pokmon to counter with (especially given the +30 weakness), Scramble and Double Rainbow Energy were still legal, some potential counters were rotated out while others were delayed for release, and so on
Cards like Scavenging Ooze target a card in a graveyard and not you as a player
Outlier sales for this card are around $7-9, but are sporadic in their timing, making them less believable