There are several vendors in Netherstorm that can make you quite a bit of gold. It is hard to get too, so it may help to use a alt that you don’t need (that preferably has the flight paths). These vendors sell a range of engineering items, vendor pets (Covered in a previous article), enchanting mats, motes, and herbs.
I have a level 70 alt that sits at one site or the other (you can leave out Area 52 if you want to cut down on time) and flys back and forth to buy things. This is something I do when I have time to get some extra spare change.
The route I use is starting at Area 52 (again you can skip this if you want) at Qiff, the engineering supply vendor. He sells Fel Iron Casing, Smoke flares, Handful of Fel Iron Bolts, and Adamantite Frames that can sell for double or more than the vendor price.
From there I fly up to Stormspire, where I visit Dealer Najeeb, the spare parts vendor. He sells Adamantite Frames, Motes, Elemental Blasting Powder, Handfuls of Fel Iron Bolts, and Hardened Adamantite Tubes. The next stop is Dealer Sadaqat, the Potent Potables vendor. He Sells Felweed, Icecap, Dreaming Glory, Mana Thistle, Netherbloom, and assorted mana and health pots.
After that, I visit the two enchanting vendors to buy some strange dust and lesser magic essence. Finally followed by the Pet Vendor, Dealer Rashaad. He sells several pets that you can make a profit off of since people don’t want to spend the time flying all the way up too Northrend.
This run can make a small chunk of change when it is added up, and only takes a couple minutes out of your day to check the vendors.
All the items are limited supply, so someone may have beat you to some of the items. Check again in a little while (an hour or so) and see what has respawned.