It does a hell of a lot for a single green mana
When they do, bidding wars follow
Generally those decks have very few coloured cards and those that they do have are either key cards to the deck or just very powerful important cards you rarely want to give up
If this isnt convincing enough, Gardevoir ex saw a commanding domination of Japans ADV1 to PCG9 sets, which equated to our ex: Ruby & Sapphire through ex: Power Keepers (RS-PK) format due to similar reasons: being able to use Imprison to lock down your opponents board, creating inescapable board states while slowly grinding out damage and taking prize cards
Youll likely see: investors rushing to lock in profits sealed holders becoming nervous newer collectors assuming the market is collapsing panic selling in certain products And when enough people do that at once, prices absolutely will fall
It's also worth noting that some cards have been reprinted at different rarity levels in different sets, so two copies of a card may have different-colored symbols