Hello! A lot of people knows about the fact that you can buy lvl 65+ blues for 5-15g and Disenchant them into Large Prismatic Shards which goes for 15-25g (varies). That is profit, although, many people knows about this and therefore the profit will fall.
But you can still buy lvl 60+ greens and disenchant them into Arcane Dust(1g each and each DE will earn you about 2.5) // Greater Planar Essence (going for 5-8g and each 2 greens DE'd will earn you 1).
Same is with lvl 40+ greens that disenchants into Greather Nether Essence
That was all, hope you liked this small guide //hug