I am still making a nice profit on cutting Epic Gems; and no - I don't mean Cataclysm ones.
I like to pretend that only twink toons use Northrend Cataclysm Epics; bonuses for twinking toons using gear with sockets or possibly a belt buckle. This makes sense; a Northrend gem can be placed in any gem slot regardless of level of gear; best upgrade available. The last time I checked however, way too many of my Northrend gems were bought by Lvl 85 toons in cataclysm gear (where a cata rare is better than a northrend epic)
Similar buying patterns exist with Northrend rares; cut Reds sell better; followed by cut Oranges; followed by the rest. However, I pay little attention to what is most likely to sell; and post the lot.
I am currently posting these gems for between 200-400g; and have very very little competition (so it is most often posted at 400g)
Supply is a solvable problem. On my realm, there are not many northrend miners; for a while I was prospecting saronite and titanium ore; making icy prisms (from the uncommon gems) and transmuting the rare gems (converting frozen orbs into the required element). However, this often left me with insufficient supply.
However, many players have an excess of justice points. 220 Justice points buys 1 uncut Northrend Epic; from the JC shop in Dalaran. I have been paying players between 100-130g per uncut gem (depending on my current supply); generally selling cut gems for ~350g.
For those without patterns, they are bought with tokens; (Northrend JC dailies etc); but you then have to choose between JC cuts and dragon's eyes (resold on AH as nightmare tears).
Some patients is called for; and I try to only cut what I will immediately put on the AH (for bag space reasons as much as anything).