My plan was to level woodworking. The primary reason for doing so is so I could repair fishing rods (Lu Shang's in particular) but I haven't exactly been fishing up a storm. My woodworking is at skill 10 (of 100) and I wanted to make some acid bolts to skill up. It turns out no one sells the materials to make them anymore and they take alchemy 45 to make. So, in order to level woodworking from 10 to 15 I decided to level alchemy from 0 to 45. Almost makes sense if you don't think about it too hard. My alchemy is up to 41 now and I can start in on the acid bolt heads.
The surprising part, to me at least, is I made an awful lot of money getting my skill up to 41. The way crafting works in FFXI is almost everything has a 'high quality' result that you can only really get when you've leveled well beyond the needed skill. For equipment this high quality result tends to be a strictly superior version of the item. These '+1' items tend to sell for a lot more than the material cost. As such, high level crafters would make a bunch of the normal versions of the item in the hopes of getting a +1. They'd get all their profit for the +1 and then would just liquidate the normal versions for whatever they could get, typically substantially below cost. Couple this with the fact gear doesn't bind on equip (and therefore can be resold to another player when you're done with it) and skilling up by making dozens of the same piece of gear is a huge waste of money. (Well, you get skill out of it, so maybe it's more an investment than a waste?) For stuff that comes in stacks (like arrows for example) the high quality result would just make more of them. So a high level crafter making a consumable would just be more efficient in terms of cost per item. They could afford to sell for less than your cost because it could be well above their cost. Couple this with the fact there used to be a bustling real money trade business in FFXI (and therefore 'Chinese gil sellers' who were willing to make all the consumables for moderate profit) and skilling up on consumables was a huge money sink too. Sometimes you'd find a recipe that would sell well to a vendor and break even but mostly skilling up cost money and lots of it.
Square is currently in the process of releasing mini-expansions to raise the level cap in the game. It was 75 for years and years and years but they're now on their way to raising it to 99. (They're at 90 right now.) There used to be insanely powerful items that cost absurd amounts of money that people would hoard gil to buy. Now, that stuff is not as good as stuff that drops in the expansion zones. Also the new zones generate a lot of currency just having people level in them so there's a lot more money to go around amongst high level players. This means that someone who may have been happy crafting for profit before (because they needed to save up for a relic) now have no incentive at all to do so. In fact they probably make more money buying consumables and just farming in the new zones. So the consumable market, at least, is wide open. I found a recipe to skill up on, for example, that was worth about 5 times the material cost and sold almost instantly. (The materials come from vendors in 3 different cities, so really not worth a high level player's while.)
I'm now wondering if I should give up on the woodworking plan and just keep leveling alchemy. I should take a look and see if there's anything a high level alchemist can make that I really want. (I think they make bullets for corsairs to shoot so if I end up playing a corsair I might want that. Who knows?)