This spam is exactly why I think they should have added a global message cooldown instead of increasing the cost to 5000 gems. It hurts the poorer folk and doesn't really affect the richer ones. Now that the cost is higher, less people are global messaging, and the ones who spammed, still spam. I think I'm speaking for everybody here, please revert the global message price and just add a few minute cooldown instead.
Tldr: High message cost ≠ less spam
Global message cooldown = less spam