Slate has an article on making staples from scratch. The author finds some (making bagels) are cheaper and taste better, some don’t work (making cream cheese), and some (making jam) just taste better.
After a failed experiment in bread, I know making things you normally buy can be harder than it seems.
I do refuse to buy pasta sauce. I either make tomato completely from scratch or start with crushed tomatoes. For cheese sauces, I start with a roux and go from there.
I will be trying bread again and maybe bagels, too.