Every time a crafter attempts to make something, there is a chance we won't HQ (unless you have a 100% HQ recipe/crafting set, which is pretty hard to get). If an item is worth X, and has 90% to HQ, you have to factor in that 10% chance of ending up with a loss when you calculate in in your average profit margins, otherwise, you're better off just selling the mats.
With some melded gear all 2 star items are 100% hq rate. There is no chance to nq if you have all the crafts leveled. I have never nqed a 2 star item because the chance doesn't even exist if you know what you are doing.