With the release of classic now is the time to repeat a very important idea in goldmaking. Always consider the best use of your time and materials to make sure you are actually getting the highest profit you can.
This is a concept that will likely be familiar to many of you. Opportunity costs are used in economic decision making. It is the “cost” of a lost opportunity. The most common example of this in WoW is of course when valuing materials you have farmed yourself that you want to craft with. If you have 3 Ghost Mushrooms that you farmed and they are currently selling for 1 gold each, and the Elixir of Shadow is selling for 2g80s then the opportunity cost is the 3 gold you get for selling them separately. In this case you shouldn’t bother crafting the elixir.
Materials have value even if you farmed them yourself
So many players suggest pairing gathering and crafting professions. And while it is true that your materials will cost you way less gold to acquire, you will still be foregoing the value of the items. You should really evaluate farming and crafting separately. Value the farming based on the market value of materials, and the crafting based on how much the materials cost. Then you can make sure that you only focus on the most valuable farming or crafting.
This is why all my TSM settings use 120% crafting as the minimum price for crafted gear. I buy all my materials, and I only craft items if I can make at least 20% profit even if I buy the materials off the AH.
Only farm if you like farming
My experience is that farming only makes sense if you enjoy it. Getting sizeable results requires that you put in regular sessions with decent length. Make sure your farming is actually optimal if you want to do it. Having a gathering profession to just pick stuff randomly can get you some start up capital, but ultimately it is insignificant compared to a second crafting profession.
Farming is really not necessary for gold making, and in fact you will most likely be significantly more time efficient if you stick to crafting and flipping.