It's hard to do this. There are often just too many people supplying. It works to a certain extent with glyphs, with volatiles I had some luck. I did make some money over a certain period, but in the end I just gave up. Now I'm just buying out volatiles that are listed so cheap that they are almost at the volatile life prices as I generally view my time to do the transmute would be equal to the extra gold I pay for the other volatile.

On my server the Darkmoon Cards of Destruction are so low in price that I don't even understand why anyone is doing them. The Earthquake decks are going for 3-4k. The cost of making them are close to 800g per card. So I don't even understand why people bother making the decks. I'm thinking that the problem is that I'm on a medium population RP server. I got out of that market with a huge "loss"(just decided to keep the one deck I made for my self, and sold off the remaining singles for a bit of a profit.)

On my server glyphs are the big money makers, and here I do try to control the market of all glyphs with a 75g+ profit, and it has worked. So far....... The next big profit are the enchants(both regular and the leather/cloth ones), but the sales are fewer. Bags are sometimes profitable, but often people are selling at a loss. I do make some money with disenchanting.

I am baffled that someone would sell a epic cloth piece for 200-300g profit when you can only make about 1 a week, and they do not exactly move like hotcakes.