Earlier quoted context omitted.
Even with in the exact same product but different sizes I seem them use different units to make to hard to figure out which size provides the best value
That seems odd to me. Wouldn’t the store want you to purchase the bigger product, and thus spend more money? You’d think it would be in their interest to display the per-unit price comparison, to emphasise where a bigger package is better value.
I know of several products that the Mid Size packaging has the best Per Unit value.
And several where they are the EXACT same price per unit, so they want to push you to the bigger one hoping you will waste most of it.