For health and environmental reasons I started to use basic ingredients rather than buy the 'manufactured' food product - but I've been shattered by how much you can save. Basically you end up with really excellent, organic, food for less than the 'non-branded' equivalents in the supermarket.
A crockpot (around £20) means you can cook your own:
Red kidney beans and all other beans
Chickpeas (so hummous)
You can buy milk and cream from organically-reared, grass-fed cows and make:
Yoghurt
Greek yoghurt (the supermarket stuff isn't real Greek yoghurt anyway)
Crème fraîche
Paneer
Butter
With a decent food processor you can make:
Tahini
Coconut milk
Mustard
Curry paste
Stock
Nut milk
Flour
the list is endless. It's all either cheaper or the same price but the quality is vastly superior and you know precisely what's in there. It's also, amazingly, often quicker - but I do have a Thermomix so this may not be quite the case with other processors.
It's just like with the programmes other posters have mentioned ('Shop Well for Less' etc.) - it may be a relatively small amount on one individual item, but it adds up to huge savings every year.
As for the taste, knowing that what is in your food, and the sense of satisfaction that you've made a dish genuinely 'from scratch' - nothing beats it.