Enchanting Cataclysm gear takes Hypnotic Dust, Celestial Essences, Heavenly Shards, and Maelstrom Crystals. I've spent the last week making and selling scrolls, and this has led to the discovery that these materials are not currently being used in the ratio they're being made. Celestial Essences are, by far, the bottleneck.
This is not a scientific fact, but I sell a lot of scrolls, and that means that my materials use is probably a representative sample of my market's actual materials use. If you simply look at all the enchants at ilvl 300 and up, the ratio of materials used will be different than if you look at a sample of actual market data. Actual market data will include the fact that some enchants sell better than others. One could, however, take a look at Wowpopular.com's enchant list and weigh each recipe by the number of stars they give it to get a general idea.
That said, let's look at the best and cheapest ways to make Celestials.