Look on the back of basically any tomato-based product and you will see the words "tomato sauce (tomato paste + water)". It then goes on to list seasonings (it usually just says spices, dehydrated onion, HFCS) depending on the product. That's right. Tomato sauce is tomato paste and water. You can literally buy a can of tomato paste and add equal parts water and get the exact same product minus some flavoring.

"Why would you do this," you ask. "Is it cheaper?" I've seen tomato paste go on sale when the date gets within a year of it's sell by. Tomato paste is often not thought of as being an ingredient that can stand on it's own. I see recipes all the time that call for both tomato sauce *and* paste like you would need them both. Does this attitude contribute to it's sales? I can't say for sure, but it seems so when it's reduced to 50-75% off. A 12 oz. jar of tomato paste can produce 24 oz. of tomato sauce. That's not bad for $0.50 or less. Add some sugar, olive oil, garlic and onion powder, and some dried herbs, and you have a can of spaghetti sauce that retails for $0.99.

"Okay, it's cheaper...when it's on sale. Why else would I buy it?" Versatility. If tomato sauce is just tomato paste and water, why buy both tomato sauce *and* paste? You'll have to store both. If you find yourself adding things to the canned/jarred sauces to improve them, or wish that, say, it had less garlic, you can begin with a clean slate.

"Cheaper and more versatile. But I have to add spices and it's more work." Well, perhaps something could be said here, but I don't really know. I guess this doesn't apply to you after all.

Why the long post? 1.) to be informative and 2.) to inquire about if anyone else has thought of this and 3.) more ideas for using tomato paste

tl;dr Tomato paste and water are the source of nearly every tomato-based product. Recipe thread.