I add frozen vegetables to a lot of things to bulk it out. Some examples include frozen spinach to pasta sauce or frozen broccoli to Rice-a-Roni-type meals.
The most historical filler is starches to stretch a protein. A smaller serving of meat goes a long way when served with rice, pasta, potatoes, etc.
Consider how to fill a meal as well as individual ingredients.
Dried foods are the best value, I would experiment with that. Rice is famously filling and cheap
In the same area, beans and lentils can be added to everything to stretch it out including the aforementioned rice lol. I feel like everyone knows this by now though. Frugal staples are dried bulk rice and beans
Dried mushrooms are also significantly cheaper than fresh.
Try to investigate why you're paying more for homemade, because that seems odd. Are you doing per ingredient price breakdowns? Identify how you're losing out and troubleshoot that in your recipes.
When I make something more expensive than store bought, I try to make sure I know why I'm doing it. I don't trust a lot of food additives, my mindset is the price you pay with cheap food isn't in your wallet.
Maybe dried shredded coconut in your ice cream?
In most cases its just the economy of scale at work. I cant make a pizza for what Dominos can because they buy every last one of their ingredients by the tonne.
A simple margherita is cheap to make from scratch. the toppings are the real killer.
Mainly when I created this post I was thinking of cookies and peanut butter, but also presumably ice cream. Probably a McDonalds smoothie is also cheaper than a home made smoothie (if we're just looking at $/ml).
Granted cookies can be done cheaper, but when I made cookies on my own for the first time I was shocked by the butter content. Could buy a pack of low quality cookies for the cost of the butter in a 12 cookie recipe.
Don't know about ice cream, but adding mixed frozen cauliflower to chocolate milkshake is invisible to the taste for me (and I am a picky eater) and I find it much more filling. Some spinach work too but you can add too much before noticing it by taste/smell Even at a third, cauliflower is still invisible to me in comparison.
I will definitely be doing this in the future. I loove smoothies.
Foods with more water in them are more filling. Grapes fill you more than raisins; soup more than a roast.
Fiber (and fat) also makes you feel more sated; I always load a sandwich or taco up with greens for that reason.
Iake.my own almond milk. I save the part left behind after squeezing out the liquid. Lay it out on a tray and let it dry, send it through a blender till fine. Free almond flour! I add it to my pancake mixes and baked goods for extra protein and so I don't use so much regular flour (or pancake mix).
Bananas are probably the cheapest thing you can do to stretch ice cream. Make a lot of banana splits.
Potatoes can bulk certain things out pretty well. Probably not ice cream--but you get the idea. (...probably. But maybe cooked and pureed sweet potatoes could?)
Discuss how to save money.