I switched the other day to a 1000W - 7200K MH to try it out as a finishing bulb but was running a 940W Hortilux conversion bulb up 'til then. I have 400W HPS ballasts as well but needed the 1000 for this crop. That 940 was $170 and I've seen them for almost $300 but now have a MH/HPS 1000W ballast so can replace it with the much cheaper regular 1000W Hortilux Super HPS bulbs that go for around $100.
All my ballasts are magnetics as well and some are 40 years or so old. Wonder how many digital ballasts even go 10 years. Not the cheap ones a lot of guys buy off Amazon I bet.
Good LEDs are still way too pricey for me to think about switching and in my cool basement I need the extra heat I get from HID lights tho I wish power was a lot cheaper than it is here. Almost $90/mth to run a 1000W light 12 hours a day.