Unit Price vs. Total Price: Why Unit Price Is the Fairer Comparison
Total price alone doesn't account for how much product each package actually contains — a package with a lower total price can still be the worse deal if it also contains proportionally less quantity, which is exactly why unit price (total price divided by quantity) is the fairer, more meaningful basis for comparing two differently sized packages of the same product.
This distinction seems obvious stated directly, but total price is still the number most prominently displayed and most naturally noticed while shopping, which is exactly why the comparison trap is so common.
Why total price alone is misleading
A $3 package and a $5 package of the same product look like the $3 one is obviously cheaper — but if the $3 package contains half the quantity of the $5 one, the $5 package is actually the better value per unit, a conclusion invisible from total price alone.
A worked example
A $3 package containing 6 oz works out to $0.50/oz. A $5 package containing 12 oz works out to about $0.42/oz — despite costing more in total, the larger package is the better per-unit value, the opposite of what comparing total prices alone would suggest.
When total price is still the right number to look at
For a purchase where you specifically need a fixed total quantity (not more, not less), total price for that specific quantity is what actually matters — unit price is most useful when the goal is finding the best value per unit among several package size options, not when quantity is already fixed by a specific need.