Recently in a WoW gold blog that I read, marketsforgold, croda has touched upon his theories behind how to evaluate your gold flows. I really suggest reading what he writes, it's very interesting. I find this topic really intriguing so I figured I'd put my 2 cents in. For most of this post I'm going to use a base example, I've chosen Inferno Rubies because they're a gold making favorite of mine.
So how much is your Inferno Ruby worth? Let's say you can buy uncut Inferno Rubies on the AH for 150g each, and can sell the major cuts for 195g. This means that the act of cutting the gem is worth 45g to you (ignoring AH fees). Let's take it a step farther. You decide to buy 100 stacks of Elementium Ore for a reasonable price and prospect it. Luckily you also have a Transmute Master alchemist who can transmute your extra Carnelians with a few Heartblossom to more gold making Inferno Rubies. Doing the calculations, you estimate that it's costing you 60g on average to make an Inferno Ruby. So the action of prospecting and Transmuting is worth 90g per gem.
In both these examples you are taking less valuable items and adding value to them by using your profession(s). You're doing a service for someone who doesn't have the profession. You spent your time leveling your profession to 525, they didn't, so you rightfully charge them for your expertise in the area. ON TOP of that, you're going out of your way to gather the materials, craft them, and post the finished product on the AH. Therefore you deserve much more than that measly tip they'd give you if they found you via trade chat.
Gold Per Hour
In croda's recent post Measuring Gold Per Hour he outlines how he evaluates his time spent making gold. His overall strategy is great, which he summarizes at the end, it's well worth the read. What I do is a bit different. I don't care how long an item takes to sell on the AH, I craft based on what's in my inventory, ordered by most profitable professions. Unlike some of you though, I always have enough professions to keep me busy. If you're new to a server or the game in general you may only have 2 maxed professions. Basically I organize my professions (loosely) via this flow chart which is based on my servers economy (yours may differ):
Cutting Gems > Prospecting > Alchemy CDs > Inscription > Enchanting > Tailoring > Cooking > Farming
Again, this is a loose, but mostly accurate priority order as far as my actions go. I like to keep around 40 of each (Delicate, Brilliant, Bold) Inferno Ruby cut in my poster's bags at any given time, so I'll cut raw gems I may have sitting on my JC. If I need more gems, I'll prospect. Then I go back to the beginning. Okay I cut the gems now, so I don't need to prospect, better do my Alchemy CDs, okay got all that done, log on to my scribe, and so on. Again this is a loose guide but usually how it goes. My method is based on what I have to sell not how long it's going to take to sell (A great example of this is in my post Flipping Twink Gear), but like I said I really never reach the end of the list so it's not a problem for me, there's always SOMETHING to do.
AFK time is something well worth evaluating. The most notorious Profession for having AFK time is Inscription (Granted you mill your own pigments). After milling all your herbs you are going to craft 500 inks. GO AFK! You have other things to do, you don't need to watch your character craft inks. Take this time to do something that needs to get done outside of WoW. Now you're being productive IRL and in WoW. It's a win win! I personally don't consider this time as time taken/lost to crafting. Even if you're about to go out, just log your scribe, hit Create All and leave! Worst thing that happens is the game logs you out before you finish and you have to do it later. Whether you're grabbing a glass of water, going to the bathroom, or maybe tabbing to read your favorite gold blog (hint hint), take the time to get away from WoW for a bit.
That's all for now. I think there is more I could say on the topic, but for the sake of people actually getting through the whole post, I think this is a good stopping point. If you have any questions or would like to see a post about a specific topic, post a comment asking for it!