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 polic

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.