I spent 300g on greens to DE off the AH. After a quick De sessions I ended up with 54 infinite dust (4.4G), 11 Greater cosmic Essences (15G), and 2 Dreamshards (20g). So that generated 442G worth of mats for 142G profit. This market is usualy highly picked over. I ran the same scan 4 hours before and only picked up 3 items.
I did it again a few hours later. I spent 136G on 18 items. 40, 12, 5. The results was 47 Dust, 4.6 Essences, and one Dream Shard. With the same numbers as before, that gives me 295G worth of mats.
Sometimes I get very little, other times I fill my bags with items. It never hurts to check.