Why & How?
Cooking recipees sell well because they have an achievement attached to getting 160 recipees. There are only about 165 in the game, some of which are festival linked.
I have found that the 'big' recipees are alliance cooking BOE quest rewards:
For the next stage down, there are still a large number of out of the way recipees. Again alliance has the advantage as some of their recipees are not only out of the way, but also sold by alliance vendors only. For these recipees, you can often get 4 times your money back.
Some usefull links:
Wowwiki Faction Exclusive Recipee List
WowWiki Cooking recipes