The problem is, though, if your opponent can't destroy this, and you have three earth pillars in play... You win. The only event where you don't win is if you deck out before they do, which, well... It's possible to delay being decked out ad infinitum via Eternity... And assuming that you don't just kill your opponent in one of the many horrible stallbreaky ways available (Pharaoh if you're going to go with eternity, pulverizer to add some momentum... Arsenic, maybe? Pylons combo nice with SoSac.)
The problem here isn't really the cost. The problem here is you can run six of them.
Which means your opponent needs to destroy them six times... Or kill you before you play too many of them.
This is something most decks simply cannot do. Combine it with dims, and holy cow.
It means your opponent either needs to run a pulverizer, an earth/gravity duo card, something not very many decks can run... Butterfly Effect, one of the worst cards in the game, or six copies deflags or steals, something that no rush would ever do.
Essentially, it's dims on steroids; With dims, if you can't get around it, you lose. Fortunately, that's not too difficult.
With this, if you can't destroy them all... You lose.
Increasing the cost will not change a thing, really. Well, it would, but due to how weird quanta balancing is in the higher costs (It's not linear) it won't really give a desired effect.
What you need to do is make this thing far more easier to deal with.
Preemptive edit: Don't ninja me Treldon ;~;
Yes, changing it to "If your opponent casts a spell, destroy this" should be at least a good first step.
Preemptive edit: Don't ninja me Submachine ;~;
That'd work a lot better.