The difference is even more apparent when I eat something full of empty calories (cough) McDonalds (cough). I can really feel my body reacting well to the good food and not so well when I feed it the junkier stuff. This is a good sign and the healthier feeling is definitely good motivation to keep up with it. I didn't have fresh groceries for a couple of days last week and I really noticed it.
At this point, I'm not sure if I'm saving much money but the benefit I'm getting from generally feeling better is enough to make me want to continue with it. It's pretty good motivation!
I've also changed my actual shopping habits in the sense that I only get about 3-4 days worth of food instead of trying to get everything that I might want for the whole week. This results in less spoilage (I used to get so much food that half of it would end up going bad before I could eat it) and also makes it easier to actually carry the groceries home (I used to struggle with too many heavy bags and get home feeling exhausted). Overall, grocery shopping has become more enjoyable and I don't have the worry of wasting food because of spoilage hanging over my head.