just did it and got the 100k achievement.

Levequest Reward: 99,729 gil Vintage Doublet Vest
Faction Bonus: 9 faction Credits 485 gil
Completion Reward: 894 gil
Difficulty Bonus (4 stars): 1,166 gil.

so in total i got 102,272 gil and the achievement popped.


So for future reference.... YOU CAN GET THE ACHIEVEMENT WITHOUT THE BASE REWARD OVER 100k.