Between the implementation of Inferno, and the recent patch that flipped the payout system, Faction War pilots plexed roughly 7.8 Million Victory Points.
At roughly 20 Victory points per plex, that is approximately 390,000 plexes.
If we assume that around 75% of those were LP-paying offensive plexes, and that an even number of minor, major, and medium plexes were run, that comes out to about 5,118,750,000 LP.
At an average of 5,000 ISK/LP made, that is approximately 25 trillion ISK.
If 75% of those people were cashing out on items that required both LP and ISK, that's approximately 3.8 trillion ISK that was washed down the Faction War ISK-sink's drain.
While hardly a scientific analysis, this is definitely some food for thought.