I feel pretty ripped off about this, too. I purposely held off on the Trooper dungeon and focused on other limited events since it was stated the Trooper dungeon was a permanent addition. I figured I had all the time in the world to work on those achievements. Now with the change in currency, looks like I will NEVER complete it. I still have other characters I'm trying to get that are locked behind FC. Not to mention any future characters that will be added to only the FC store that will likely cost 6-10K FC since every new character that is added is at a higher cost than the characters that preceded them. I try not to complain much about the obvious issues with this game. I mean, it's only a game, but this change was highly disheartening.