thats the catch, proper projectors are not cheap, even with mass production being more commonplace. no two vehicles are the same when it comes to projector placement and alignment, therefore each light must be custom made for each vehicle. not just each model, since the lens in the projector housing, as well as the housing shape itself, comes into play with the alignment, and they are not adjustable, a truck or suv will need a totally different lens than a car. you can aim a projector headlight, but you can’t adjust the lens or housing focus, all you’re doing is adjusting the whole housing direction to point the light. so, a 4×6″ housing made for a car, will not be properly designed for a truck with a 4″ lift, for example.
there are companies that offer custom made hid projector housings for anything that accepts any size of sealed headlight, but the cost is usually $1200-$1600 per housing, and the request forms need to know detailed measurements down to millimeters, and once installed, you can never alter ride height, tire size, etc, without replacing the housings.
ever had a new cadillac or lexus cruising toward you at night, and been blinded almost entirely by their hid projectors? chances are, they’ve replaced something with something other than stock. tires, wheels, suspension, it doesn’t matter what it is, the tiniest alteration will make that hid lighting system dumpster worthy. most of the cars that come factory with hids also either tell you in the fine print of their owners manual, to always distribute loads evenly front to back, side to side, or, they have built in load leveling suspensions.