While chromatherapy may be a nice, premium feature, who says it's mandatory for a steam shower? ANd, the need for any specific water treatment for the steamer may or may not be required - the house may already have soft water and is fine for the unit, so you'd then drop the cost down considerably. 35' of 8g wire (the gauge will depend on the size of the unit you require, but 8g would supply enough power for up to about 150sqft from at least one manufacturer) is easily less than $100, plus maybe $30 for a CB, and then the labor, which could be all over the place, depending on the layout, but probably not more than a couple of hours - around here, about $150.
Certainly, you CAN spend a huge amount more for a steam shower over a conventional one, but other than tiling the ceiling and using a membrane all over verses up the walls and then the steam unit...the difference in cost really isn't a huge amount. Certainly, you COULD spend a lot more, just like you can buy a Rolls Royce, but a Hyundai will get you from point A to point B, too, and they have some nice vehicles as well. Depending on your choice of membrane, it may already be well suited for a steamer.
While there certainly are people with a budget for a $40-50K or more bathroom remodel, you can get a perfectly serviceable one for a lot less. It won't have all of the custom frills, but they play little part in functionality - nice, maybe, required, no. It does take some careful planning, and good workmanship, regardless, though.