well main problem is you need them for everything lol and there is just too little to go around. From upgrading armors pretty much you can waste from 1m-100m feso if you go +8 and are not lucky lol. Enhancing weapons also takes a bunch to especially if you craft, break and repeat until you +7. Buying sedecram/ancient en celar pass is another feso sink. Buying sedatives to chip weapons/armors is another feso sink. Spamming CTB another feso sink. Buying quest warp passes/To HM LA your 100+ toons, barrack slots/socket fluxes. Pretty much the whole damm game needs feso lol and you have to buy it even if you want to or not.
Most of the the time I tell myself, im not gonna buy overprice feso but guess what you need it to progress so at the end i end up buying it even though i think is way overprice, are else I cant progress in the game.
Now use your imagination and think if I a high end player struggles to buy feso cause is so expensive, what would a new player starting out do if he has no way to progress in the game. He cant raid cause he dont have gear, he cant make new gear cause he has no vis to buy feso, so he either uses cash or quits. Or he use cash doesnt get enough feso to upgrade his weapons and armors, gets annoy then quits.