It depends on the approach. My window installer prepared everything, I just had to "slide in" and hang the motor, which was both quite easy. So this part cost me nothing except materials. Then my electrician connected the control unit I bought for a few euros (which was chosen so that it also fit into the framework planned for the socket already intended for the window). With that, I easily saved a three-digit amount per window for 2 hours of work plus a bit of time for selection and ordering.