Yeah, what Don said. My MH came from the factory equipped with the 3 camera system. I find them pretty useless: image too dark at night, washed out with the sun behind you, difficult to judge distances of vehicles behind/ along side of you. I essentially ignore mine. I wouldn't take them off but I wouldn't pay to have them installed, either.
If you think you would like them, try to get a test drive in a MH that is equipped with them. I wouldn't let it be a deal killer if I were considering buying a MH without them.