Corporations are made out of humans. They're about as eager to cut their own profits as human workers are to reduce their own wages.

Which is why we need external regulators to make sure they don't have an easy out by deceiving customers.

Or people could just stop buying Mars bars and other ultra-processed foods if they feel they are overpriced which would force corporations to adjust their policies. Mars, Nestle, McDonalds etc. will continue increasing prices as long as people keep buying regardless of how much they complain.

The pricing of normal raw food products, produce etc. is generally quite transparent.

Can't fix a systemic problem with individual actions.

Unfortunately, "external regulators" are both human, and subject to the self-serving whims of the power-hungry politicians.

Plus, nowadays, a "justice" system which might well decide that Badguys Inc. has a First Amendment Right to label and sell 10 1/2 oz. of inspection-failing mystery meat as "1 Pound Pure Prime Beef".