Warning: long read. Scroll down to the end to see the end-conclusion in bold-text

It all started about a week ago. I am an elemental leatherworker who has almost reached 300 in skill. I noticed how extremely hard it was to find hearts of fire for the right price at the AH to make a helm of fire, but i hated the idea of looking for them myself because i don't like killing the same mobs thousands of times.
So i looked at the prices on the AH to see how high i could bid on hearts of fire, while actually making profit. The first thing i did was drawing a few conclusions.wow gold

1) the price they ask at the AH for the items i need to make the helm could also be the prices í am asking for them. Which means if i buy all the items (including leather) and i make no profit by selling the helm, there's no use to the helm other than upping my leatherworking skill.world of warcraft gold
2) the helm of fire sells for 30-40 gold.
3) i need to include the AH deposit funds to my costs, as "safety-measurement".

Then i looked at the prices and i saw, to my horror, that from the moment you have none of the ingredients to the moment it's there on the Auction for buyers (looking at the lowest prices), costs me 45 gold, 38 silver and 80 bronze coins in the best scenario. Which means if i sell it for 38 gold, i will loose between 7 to 8 gold. Which is simply incredible.
Because the helm of fire is an item that needs several different ingredients to make, i know my conclusion is very close to the truth.

When i realized that, i started thinking. If the helm of fire doesn't give me any profit, what will? Next thing i did was check other prices. Because usually the same ingredients are used, the more i looked up, the easier it was to know what another item would cost. I went down my whole leatherworking list doing this.

My conclusion? Well leatherworkers, nothing gains profit. Not a single recipe.
In fact you loose money, time and a perfectly fine profession slot. So, leatherworking makes no money. Not even the 300 skill recipes do (as far as i know).
Thén what makes money? What i did next was ask other players with crafting professions if they made any money. I got 3 answers: "of course it does, otherwise what's the use?" "i never really looked at it" and the shocking one, "no. most players naturally think it does, but if you look into it, it doesn't."
These answers counted for all crafting-professions, except for one. Alchemy. Alchemy is a different story because they can change essences into other essences. At the AH, essence of undeath will cost around 2-3 gold, while essence of air costs around 17 gold.