All Bingo

While that can be true, it isn't always. Some things are way cheaper to make than to buy. Other things are more trouble than it's worth to make. People spend hundreds or even thousands of dollars on fancy cakes, but if you're good at that, you can just make your own. It also matters how much you're making. If you're going to use up the whole bag of flour, sugar, etc. baking cookies then each one will probably be a lot cheaper than if you bought them. But if you only make one batch, then it's more expensive.

There are other considerations too.

* Can you even find the thing to buy it? Much of what I make isn't actually available for sale, partly because my tastes differ from the Standard American Diet and partly because I like to devise my own recipes. I had to start making my own sloppy joe sandwich filling because it became impossible to find a canned version that wasn't lightly flavored high-fructose corn syrup. :P My version consists of a grocery bag of assorted produce cooked down in a crockpot with ground meat added.

* Can you make something as good as or better than the storebought version? I'm not going to bother making madras lentils because we can buy great ones in packets. But no restaurant has come close to my partner's lentil dal or my ginger ice cream.