I became Honored with the Violet Eye Faction running through Karazhan. What better way to celebrate being Honored than to check the Karazhan vendor, Apprentice Darius.
When you are Honored with the Violet Eye, you can buy the Inscription of Endurance, Design: The Frozen Eye and a non-binding Recipe: Flask of Chromatic Wonder. The last one caught my attention. The recipe sells for 1 gold and it is non-binding therefore you can sell it in the Auction House for more.
I checked the Auction House and I was surprised to find out that it is priced at 40 gold. Now that’s a lot of profit from something that’s readily available from a vendor, if only you know where to look. The price may change from time to time so you must not saturate the market with it. Although you also need to be Honored with the Violet Eye to learn the recipe.
Reselling recipes on the Auction House might be the oldest trick in the book to make gold but it’s still feasible. You just have to know where to get the recipe, plans or schematics. Some people are just too lazy to look for the recipes and the vendors that sell them. This need is something that you can supply and therefore make gold out of it.