They have low cost so that you can flood the board early and attack your opponent directly
Even the base printings of Gemstone Caverns are worth around $50, so no matter what, you'll be happy to open a copy, and very, very happy if you happen to open Gemstone Caverns #51.
The Pack Dust crafting system lets every pulled card contribute set-specific dust (Common 1 Crystal 50, +50% on duplicates) toward guaranteed acquisition of any missing card from that same set endgame pity that doesn't break the per-pack economy
Ive also managed to pull two full art ex cards in Blastoise and Articuno, and the highlight of my collection is the immersive art Mewtwo ex, which comes with its own cutscene of Mewtwo breaking out of containment
Question #18: What is the only five-color card not printed in a black border
Now time for the Top Ten proper