The cost of running them isn't relevant. What is relevant: being able to get more light from a limited amount of house/set/generator power, and the control over

The cost of running them isn't relevant. What is relevant: being able to get more light from a limited amount of house/set/generator power, and the control over them. They don't require a dimmer pack, just power and DMX (wired or wireless) to control their brightness, color temperature, activate special in-light effects like flickering/strobing, etc. Some directors prefer the spectrum completeness and profile from tungsten (or the ultimate, carbon-arc, which is virtually indistinguishable from the sun.) I also think there are levels of light that aren't really feasible except with carbon arc because LEDs don't like heat and that limits power density. I don't remember what movie it was, but there's a photo of an enormous balloon light - larger than an entire house - over a farmhouse somewhere in the midwest, at night. Pretty sure it wasn't LEDs as the source, but I could be wrong.