Flying mounts? The only people who can use them are engineers, and I would've assumed people would just make their own. Do they sell, and is it more profotable than just selling the mats, assuming you're farming them?

There are a few more engineering items that can sell for those who don't want to camp a vendor for a item spawn. In the outland item range, you have the Khorium Power Core, which is used as part of the Netherwing quests to unlock an additional daily when you reach a high enough standing with them. If your an alliance player (not sure of horde having any similar quests) there is another item that is required for a general quest in Borean Tundra at the airstrip (easily skipable, but still). IF anything, the Khorium Power Core can be a real cash cow since the mats are extreemly rare due to not being as rampantly farmed (fel Iron and adamantite ore tend to go for a lot if your trying to AH power level a mining/jc skill, let alone the motes needed). I only say the Khorium Power Cores can sell pretty good because if people don't want to wait out the spawn time for the one vendor that will sell one for cheap, they will go to the AH and shell out about 400-800 gold on them. There isn't a person I know that doesn't like the nether drake mounts, so business for these is relatively stable, though you still might need to relist them several times.

OMG lol I spammed trade chat for an engineer that could make the power core! Even then it took forever... I rarely spend a lot of money (it took about 4 months for me to buy the lvl 70 flying for my first 85 alt... and even then I didn't really want to shell out that much cash) but I paid top dollar for that core! I really really wanted to finish my rep grind! I think I paid about 500g for it with my mats.

@ Mycroft

It actually is pretty profitable to sell the Flying Mounts.