I go to a store where they put the price per kilo, even when it is discounted. This way, I only need to compare price per kilo with other products to see if it's worth it!
I remember shopping for kitchen roll once, one product had a per-price that was per 100 sheets, the other per roll. Impossible to decipher!
There's also a thing they'll do where two similar products in jars/tins will have a £/kg number but one will be based on the total weight (e.g. including pickling liquid) and the other based on the weight of the actual food.
if you compare products, one might say "3.24 per EACH" and another might say "0.04 per oz" or some other nonsense.