A very basic principle

Browsing through official WoW forums there's something that always seem to pop up no matter how much me and others there try to say. There's this one little thing that somehow is really difficult to grasp. Here goes, in big and friendly letters:

TIME IS MONEY

Yes, it really is. So learn it now so you don't need to do silly mistakes later. A lot of players think that when they farm materials for their professions, they are free. "I mined this myself so it's free for me!" To keep it simple, that is just not true. Every minute you are farming something is a minute you could spend doing something else. I don't mean that you necessarily should, but indeed you could be doing something else. To calculate the time spent you simply need to know how much you would earn if you'd sell everything you farm in the auction house. 

There. You're time is not free. Everything you gather, has a value. That value can be cashed out by selling the raw material and thus receiving its value in gold. Other option is to craft it into something else and by that add some more value to it. Let me make an example here. Let's say we have ten stacks of elementium ore. If you mined it, you can choose if you put it in auction house or process further. Elementium ore would sell for something like 50g/stack so for ten stacks you would earn 500g - 5% ah cut = 475g. That's the value of your time mining them. But then if you don't just sell them, but prospect them instead. The value of elementium is usually about double the raw price when prospected. Prospecting will give you gems. A lot of green quality and some blue quality gems. Then you can sell the raw gems in auction house or process them further by cutting them. You sell the cut gems, the final product of jewelcrafting for nice profit. With ten stacks of elementium, you're likely to end up to something like value of 700g-900g when processed through jewelcrafting. Why is it more value then? Well, you've obviously put some more time into it and time always converts into money. And not just the time you spend by prospecting and cutting but also the time you've spent in leveling your jewelcrafting and obtaining the recipes for cutting the rare gems. It's only natural you'll end up with more value.

The trick in gold making is to learn to calculate that how to convert smallest possible amount of time to biggest possible amount of gold. Auction house pros quite often calculate their income not just as simple amount earned, but as a value of gold per hour. It's not a way to show of how awesome you are, it's a tool used to determine most effective gold making methods. Let's imagine you have two reliable ways to make 4000 gold every day. One of them takes you 2 hours each day (literally the time you spend in front of your computer performing all the actions required to have the gold in your pockets) and the other one 45 minutes. Which one would you pick for your regular daily gold making routine?