Advantages over other professions
Jewel-crafting stinks to level without access to large amounts of ore, so it is either going to be an expensive profession or one that requires a lot of mining. And what did I just tell you about mining? So, what is the bottom line here? Most professions are standardized to 46 spell power. Now, to be sure, a lot of raiding professionals are going to choose Engineering and Tailoring, simply because of their DPS advantages over other professions. The net DPS increase you will see from min-maxing your professions probably may not be worth the time and effort. Just know the benefits and costs of Cronous gold, and choose what improves your game experience the most.