A little google fu turned up this article :
I have an excellent biography of Barbara Hutton (name escapes me now - maybe “Poor Little Rich Girl”?) She was notorious for having people take advantage of her - particularly the “hired help”. Grant noticed this when he was married to her, and set about to curtail the staff abuse. I think that’s where a lot of this came from. I’m sure his parsimony also had roots in his very poor childhood, and the fact that a lot of actors are scared spitless that the last movie they made actually will be their last movie.