Iron ore sells for 675 - 2700 at a NPC Stand... So at the cheapest making a Ingot would be 2.7k + Fire Crystal, not much of a gain when selling in stack.
Easy skill ups if you do smithing, even easier if you go mining. You can compress your inventory by making iron ingots while looking for more valuable ore.
So, you can buy four iron ores for minimum 675 = 2700g and use a fire crystal to synth, or just buy the ingot from npc for 2700. And then you go to AH and sell them at the same price? Alright you get your money back, but come on! Sheepfoe Mambo was sold for 10k in AH for one or two years ago. Why? Because people would pay more so they didn't have to go all the way to Selbina. So stop selling these at npc price if you want to earn something >.>