What would the ideal conditions for the Haber process (nitrogen + hydrogen to ammonia) be? Why are the ideal conditions not used in industry?

The Haber process is an example of a reversible reaction where the reactants react to form the product and simultaneously the product reacts back to form the reactants. As a reversible reaction progresses the process tends to an equilibrium where the rate of reaction of the forward and backward reactions are the same. Therefore the ideal conditions for this process can be deduced using Le Chatelier's principle, which states that when a change in conditions is applied to a process in dynamic equilibrium the position of equilibrium will shift in the direction such that the change in conditions is opposed. So in the context of the Haber process, the conditions which can be altered are temperature and pressure. 

The forward reaction of the Haber process is exothermic (heat energy released), therefore the forward reaction will favour a low temperature. This process involves on nitrogen molecule reacting with three hydrogen molecules to produce two molecules of ammonia. Therefore to shift the position of equilibrium in the forward direction, high pressures would be used as in the forward reaction, the number of gas molecules decreases from four to two between the right and left-hand sides. In industry, the conditions used are 450 degrees Celsius and 200 atm with an iron catalyst. If low temperatures were used, the yield would be greater, however, the rate of reaction would be too slow for the process to be economically feasible. Also higher pressures aren't used as high pressures are expensive to set up and maintain and can also be dangerous, therefore extremely high pressures are avoided when possible. Finally, the iron catalyst has no effect on the position of equilibrium. It is simply used to increase the rate of reaction so that dynamic equilibrium is attained very quickly.