It is just amazing how much gold can you make by just selling crap. Both in WoW and in real world.
Take for example this sweet ride: The Mechano Hog. The materials you buy from vendor is the gold sink. The rest of them is just about 1 -> 1.5 k g. But this baby is sold with 15 -> 16k gold and there is a demand for it.
There are people farming Stratholme (or it was Scholo) for the Undead Mount, doing arround 200 -> 500 runs, just to mount up on a city, and people to see that they own that mount. It is just like in RL. A car sole purpose is to transport you from one place to another at a faster speed than the one you would have by going on foot. Some more things apply to a car that do not apply to mounts that good. You will get more mounts for faster speed but thats it. For a car you would want to have good reliability, safety and some confort. All the rest is just vanity.
There are a lot of companies in the world that do not produce anything usefull to the basic needs of humans, but they are succefull because we like others to see how good we are doing, etc.
So it is only obvious for those companies to provide for that demand, and milk those morons.