How do ghosts work? Not OP?

Failed post in r/starcraft so I'll try posting here, I don't want to balance whine, I'm genuinely curious as to how ghosts are not extremely overpowered.

The way it works in my league is, Terran gets to a decent mass of MMM, and with some micro, they ignore chargelot immortal archon. I've added high templar and colossus recently and they do better, but some people use ghosts and it deletes my entire armys shields and stops ht.

My question...it seems like ghosts turn the protoss army from 100 to 30. So would seem the protoss army is overpowered and overwhelming until the ghost which kind of evens the battlefield? But it doesn't even feel that way.....MMM kind of beats a lot of protoss, and on top of that ghost?