economy heading for ruin....

I still don't see a problem with lower prices. So what if its harder to make
"a lot of money"? Since everything is cheaper, you have no need to gain as
much money as before, unless to quench some sort of insatiable greed.

Trouble is, not "everything" is cheaper.
If you use up 1m meso worth of potions (which have a fixed price) per hour of training, you need to make 1m meso per hour off the drops you get, to break even. Or 10m meso for that one-in-ten-hours drop.

Or look at equips. Just your normal clean 50+ armors and weapons. You can't buy them from NPC's, but their price can't go lower than what an NPC would pay for them. So the FM price has a lower limit. If deflation gets to the point where a level X character can't make enough meso (by selling drops from level ~X monsters, and after potions) to buy level X gear, the game has a problem.