A little, lesser known cash cow that came in with 5.4 are the Drums of Rage. The Drums are basically a 'lesser' version of Herolust Warp Hysteria.
The Drum pattern is a drop from around Pandaria, so you should be able to get one easy while going about your normal raiding or farming.
These drums are very easy to make, with only one Magnificent Hide required to make 20 of them. With the current price of the Hides are 186g, you can make a killing with these.
Now maths. 20 Drums cost 186 gold to make. That's 9.3 gold per drum. Seems pretty expensive, right? Well, these little lust charms sell for about 40g each. This isn't even taking into account the daily cooldown to turn leather into hides, which can make them even easier.
That's a 400% return, for such little work and little effort.
In other news, I bought a Big Battle Bear to try and flip. 75k, and hoping for around 150k return. This is my first massive purchase, so I'm hoping it goes well.
(Also added item links, which I'm excited about!)