Rehousing old lenses to modern cine standards is expensive, there's really no way around it. Every lens line needs it's own housing and mechanics custom designed, and each lens needs to be hand-fitted and optically adjusted. There can be variations between even the same focal length from the same manufacturer.
Some companies offer "cine-mods" which basically add focus gears and uniform fronts, which is obviously much cheaper. If you're mechanically minded and have access to a machine shop you can do this kind of thing yourself. A good lens technician can service lenses like these to remove focus shift, polish and recoat damaged optics and make sure the lens is optically at it's best for a lot less than a rehousing.
The Schneiders are very short, so attaching a focus gear ring that clears the camera mount is tricky, it needs to be stepped and then reading the focus scale becomes impossible. Some people add scales to the gear ring.