Tesco's own brand or jarred tomato-sauce is 75p/500g. It's just over half tomato and bulked with all sorts of crap.
The best option I knew of until now, if you want a healthy, non home-made sauce was a branded version, which doesn't have quite as much rubbish, but is over twice the price (£1.80/500g).
Today I found a far better option in Pound-Stretcher: same price as Tesco's, but over 85% tomato (mostly plain tomato, but with some paste), made with olive-oil and dried herbs and garlic puree. Not an e-number, veg-oil or chemical in sight. The worst thing in it was a dash of sugar and some salt (and even those in less quantity than the "bargain" or "own brand" sauces!).
By CW-logic, something that cheap can't possibly be better than the expensive branded version. Yet, if you want some tomato for a sauce, it's even better than canned stuff (the chemicals that leach from the can = not good) and than all-bar-one of the branded sauces (which are often £1/250g).
I myself don't use it, but my fiance uses tomato sauce and tinned tomatoes once in a while and I like to keep an eye out for healthier alternatives for him too.