This morning I collected some fel iron for my crafters… I saved 2 stacks for my blacksmith and sent one to my Jewelcrafter for disenchanting, errr prospecting =) Krys already had a partial stack of fel iron on her from a previous session, so I was able to prospect for gems 3 times. I got all expansion gems, 2 spessarites and a shadow draenite. I also got fel powder, which sells for 15 silver each.
These gems sell to a vendor for 1g, unfortunately I can’t say how much players will pay for them. On the beta server we have a vendor who sells cut gems for 3.6g each, I assume so players can test them with their armor. Since his name is Edward the Temporary, I’m guessing he won’t be around for release and the cut gem market will be player driven.