If there is one food item that anyone can absolutely make better and cheaper themselves, compared to the store-bought version, it's tomato sauce. This is partly because fresh ingredients will almost always be better than a sauce bottled and shipped across the country--but it is just as likely that it's because most tomato sauces are pretty awful.
Belle and I eat a fair amount of pasta, since it's a quick, vegetarian-friendly food. So we've tried, at one point or another, a lot of different store-bought sauces. At best, they're inoffensive, and at worst they're flavored in exactly the wrong ways: sour, chemical-tasting, and mealy. One day, after having a particularly bad batch, I decided to try making my own again. It turns out that it's much easier than I expected, although it does take a bit of time.
I'm sure you can find a detailed recipe elsewhere (I typically just buy a bunch of produce and wing it), but the basic process of making sauce (according to the Joy of Cooking) is a simple, three-step process:
The difference between this and sauce-in-a-jar is striking. It tastes like it's made of real vegetables, for one thing. It's no doubt healthier. And if you do it right, there's no excuse for it to be bland. Give it a shot, and I think you'll agree: life's too short to eat store-bought sauce.