I started out costing the perfect cuts as 10x uncut price but have since realized this is wrong on two levels. First, uncut gems don't sell well and secondly, by cutting the gems you are costing yourself an opportunity to make the green gem jewelry (Ornate Band and Shadowfire Necklace). This is best explained by an example...
On realm, the purple and orange perfect cuts outsell the other colors by a large margin, so I am left with a giant pile of Red, Yellow, Green and Blues even after I restock the few cuts of those that do sell. There is nothing profitable to do with those gems in bulk other than vendor the cut gems (85s). On the other hand, if I make the 415 jewelry and DE I can use and/or sell an almostunlimited supply of enchanting mats. From the last batch of 100 415's I DE'd I got 175 dust, 21 essence and 4 small shards. On my server that works out to 18 gold per ring less the cost of the selling is about 16.8g per piece. Subract the vendor value of the cut gems (.85) and the 415's are worth about 14.25g.
For every excess orange or green perfect I craft (costing ~10 uncut gems), I lose out on making 1 piece of 415 or 14.25g. If it costs 10 uncut to make one perfect that means that every excess perfect is costing me 142.5.
Therefore, when I am cutting oranges and purples in excess of the other colors I need to be making 142.5g for the perfect cut or it isn't worth my time. For some cuts, I am averaging close to that much (eg willful, inscribed, fierce and tense) and I should continue making those, but my conclusion is that I need to raise my minimum price on some of the heavy sellers like the reckless (77g), deft (83g) and the purfied (86g).