Not everything in WoW can or will yield the same amount of gold per hour. There are a number of reasons for this, such as only a certain amount of demand for items, only a certain amount of materials, or only a certain amount of time. Crafting and posting various blacksmithing items could be viewed as an insane G/hr rate, considering I can smelt the ore and craft the items in under 5 minutes, for thousands of gold of profit. Yet only so many of these items sell a day, or every several days. So you have to progress to something else. If you are lucky enough to have cheap ore on your server, you could conceivably carry the shuffle even farther, yet eventually you will hit the same wall of either market saturation, or a lack of materials/time. This can be carried even further. In addition, most of us don't have unlimited time. Thus making the most of our time is important. If I only have 5 minutes, I'll check the AH, and repost items. 10 minutes, and I'll fish out the fire pools in Hyjal, and do a round of mining out obsidium ore, and look for Blazewing. (NPC Scan FTW, got this guy twice for a 1500g/item) 15 minutes, I'll check for TB, its a fast 400-800 honor for a win, esp. with the weekly quest. And so on and so forth.
A major key to becoming a real goblin is efficiency, not only in budgeting time, but also in spending the time you have wisely. Example, I prospect ore as I level up my JC in instances, in between pulls and such. When I'm waiting during break in raid, I repost on the AH, and fish out lava pools. I use addons such as baudbag (amazing addon for bags/banks) Postal, and auctionater to help organize and speed up posting/tracking.
As the Goblins say, "time is money, friend". Time you spend farming herbs or ore is not "free". Just because you gathered it doesn't mean you should value it less then market value. There is always an opportunity cost.
All in all, becoming efficient is one of the most important steps you can take to becoming a gold mogul. Knowing how to do things quickly and efficiently will even help you decide if a certain gold making method is for you. Sure, vendor pets may be sellable for 50-100g each, but if it takes you 20 minutes to buy them up and post them, is it really worth the time unless you are already in the area?
Just a few thoughts on my take on efficiency. Becoming efficient is a whole new mindset.