[indoordin0saur]

If you do the math on the theoretical maximum energy efficiency of turning iron into gold we'll never be able to do it cost-effectively until energy becomes cheaper by like 10 orders of magnitude. That's why heavy metals all come from the most energetic processes in the universe, like supernovae and neutron star collisions :)

[cyberax]

Well, you don't really need iron, lead is good and abundant enough (since it's the first stable element at the end of the decay chains).