Yea, HPS/MH bulbs are quite cheap ($10ish) but its the reflector and ballast that are quite expensive.
But i am able to get 4-6 42Watt CFL bulbs (2700k and 6400k) so i think this path is better, especially since i can use both the 2700k and 6400k at the same time (say 5 6400k and 3 2700k for...