The rarity of ferrystones is a think a product of their attempt at mtx. I know you can buy them for 10k each and then spam the inn until they replenish, but for a long time that’s kind of a lot of money. I’m level 43 and haven’t really found a solid way to make money “quickly” that isn’t just “do story quests” or “grind out mobs for maybe 500g every 2 mobs.”