Mazumok has found a small and irregular market for black dragonscale shoulders for about 100 gold--which means that there's no profit in buying 45 black dragonscales from the auction house at 2g each for a set of shoulders.
But Maz encountered someone selling black dragonscales at 17 gold--and so bought 9 stacks. Selling those as shoulders has made him about 150-200 gold.
He's been making more profit, though, by teaming up with a tribal leatherworker guildmate who can make devilsaur armor. Maz goes on a devilsaur safari for a while. Aurochs makes gloves and leggings, we split the proceeds. This has made me at least 100-200g with just a few devilsaur safaris.
Devilsaur safaris are a very different experience than The hardest part of devilsaur safaris is finding the devilsaurs, because they roam widely, where black dragonkin stand fixed. (And devilsaurs are far more sneaky than one would expect a five-story monster to be.) And the devilsaurs' paths often takes them through other monsters, so you have to be very careful of the setting in which you engage them; black dragonkin usually let you set up a good pull (except for the occasional black drake flying through). And killing devilsaurs always produces devilsaur leather--but rarely anything else of value. Black dragonkin only yield black dragonscales about 15% of the time (and you need a lot more of them for their recipes than the devilsaur leather required by devilsaur recipes), but you get plenty of silver, you get nice green items, and you get enough rugged leather and other leatherworking materials that you're rarely short of those for crafting.
Maz is now a thousandaire, and already has an epic mount. I have no idea what he's saving up his money for, besides the fun of being rich.
Amalefica collected a lot of materials and got an escort into Uldaman to train all the recipes from skill 225 to 250 in one fell swoop. My planning was inadequate, though--I didn't have some of the cheap enchant-in-materials recipes that I thought I had, so I had to teleport out of the auction house, borrow 30 gold, and buy more materials for the training.
Now, though, she's finally at the point of being able to do enchantments that people actually want enough to pay money for. I don't spend much time spamming trade channels offering enchants; instead, when I'm logged on in a city, I'll respond to anyone wanting to buy enchantments, and switch characters if we come to a deal. (The SellEnchant addon has proven invaluable for looking up Amalefica's skills and materials when I'm logged onto another character.)
I usually work just for materials and tip, without worrying too much about price--because I've found that it's common for people to give a bigger tip than I would ask as a profit margin. I've even suggested a lower price than initially offered once or twice. In doing this, I've built up a clientele of folks who come to me for repeat business.
After months of being chronically impoverished (Maz had sent her 30g over that time) and a pricy spending spree to train up (30g from Maz for training materials, another 25g from him to buy the Fiery Weapon formula), Amalefica is now making good money. To my pleasant surprise, it appears that she will be able to buy her own mount at level 40, instead of having Mazumok buy one for her.
My cursory analysis is that enchanting is one of the most profitable endgame professions, because even when people are getting all their gear from exotic drops in high-end instances, they still want enchantments on them. On the other hand, it makes up for it with crippling poverty on the way to the top.
Of course, the really big money in enchanting comes from the recipes that are extremely rare or require huge amounts of reputation grinding. Amalefica may end up doing a whole lot of grinding.
Mahotala has been given little attention of late. He's learned the recipe for arcanite transmutes, which doesn't require much play time. dvarin was right about the difficulty of making money advertising arcanite transmutes, though; he wasn't getting much business with his ads, and he wasn't getting paid much when he did. He's making more profit by buying the materials and auctioning the arcanite--but that means that a lot of his wealth is tied up in illiquid arcane crystals at any time.
For Rajana, I tried the approach I've read of taking two gathering skills instead of taking any craft skills for the early game. She started with herbalism and mining, but switched from mining to skinning because two of her usual teammates are miner/engineers.
Gathering (and auctioning everything) has made her very rich. She has about 45 gold at level 25; it seems clear that she'll be able to afford her mount at level 40 and help her friends with theirs.
Being this rich has settled my prior waffling about whether to compete with my crafter friends for resources. When I team up with friends who are alchemists or leatherworkers, I let them gather until their packs are full, and offer them any resources that I have in my bags. There's no reason to regret my generosity.