Simple... don't buy it.
A recent example is a well known brand's ready made spag bol for kids. The salt content and additives where very high. The price was £2.75 (I think) per portion, each one microwaves in 3mins...
In ten/fifteen mins I could rustle up an easy tomato sauce and cook some pasta at a fraction of the cost and it would be much healthier.
Saving those few minutes in cooking time cost about £4.00 and filled the kids with unnecessary crap.