Money making in Vana'Diel is like in RL -- not that easy. I personally think economic disparity -- gap between the rich and poor -- is quite large in FFXI. Gil buying does fuel the problem in certain extend, but I think most inflation is driven by the really rich players, former fish botters, and decrease of farmers of basic synthesis materials (like Beehive Chips). FYI, I believe selling to vendor (mostly from fish botters) are the biggest source of new money in the game, and introduction of new money in the game drives inflation.
Most of the richest players (cough Ete, Flutist etc cough) in the game tends to have one of big crafts leveled (Clothcrafting, Goldsmithing, Smithing, Woodworking). I was surprised recently how much money chocobo digging can make (learned from a long time digger). Cooking and Alchemy are the bottom feeders, but tends to make your life very inexpensive and efficient.
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Amanada (Cerberus-Retired) (aka MaiNoKen/Steven)
-- Thank you for the fun times in Vana'diel
Art for the sake of art itself is an idle sentence.
Art for the sake of truth, for the sake of what is
beautiful and good — that is the creed I seek.
- George Sand
A designer knows he has achieved perfection,
not when there is nothing left to add,
but when there is nothing left to take away.
- Antoine de Saint-Exupéry