My 400 watt MH/HPS conversion system cost me 170 for 2 hood hangars, 1 MH bulb, 1 HPS bulb, the hood, ballast, and a timer.
I know they make 250 watt HPS as well but I dont know how much they cost.
No, they dont sell them at Home Depot or Lowes. You would have to get it from a local hydro...