The prices for green gems are currently very low on most servers, especially the cut ones. This is probably because jewelcrafters use a lot of these to level up, and you can find the cut versions of Azsunite, Queen's Opal, Skystone and Deep Amber really cheap on AH. What you are looking for are gems that are cheaper than 1/100 of Obliterum, so that if you buy 100 of these gems you can make one Obliterum and seel it for a profit.
Some stacks of 100 gems can seel for as low as 3,500g, and on most servers it's a nice profit to obliterate these and sell one Obliterum. Make sure you read this guide as to how you Obliterate super quick, so you don't have to spend a lot of time doing this manually.
If you are a JC yourself, you can even buy the uncut gems, cut them and obliterate them. However, the uncut gems are usually more expensive, since a lot of people buy these to level up their profession.