It’s not for saving money. Rolling shutter sensors have better dynamic range and better light sensitivity (e.g. BSI is only possible on rolling shutter sensors).
Rolling shutter sensors can also have stacked RAM which results in very, very fast readout and cancels rolling shutter artifacts.
Even on non-BSI stacked sensors rolling shutter results usually in better IQ because it's a "simpler" pixel and readout logic.
Global shutter is more a feature for machine vision sensors only now, where artifacts are not tolerable because you are processing the image assuming absolute and precise temporal locality in each pixel's information and acceptable image quality for those products has flatlined the last few years on ~60% QE and around 15ke- FW.
