Comparing Prices Properly
The cheaper item is often the one that costs more per use, per gram or per month. Working out the right unit before comparing is the whole skill.
What a learner can do afterwards
- Compare two products by unit price rather than by shelf price
- Work out the cost per wear or per use for something bought once and used often
- Spot one offer where buying more does not lower the unit price
1 · Read
Shelf prices hide the amount. A big pack can cost more yet give you less for each gram. The fair number is the unit price: total price divided by total amount. Work it out in matching units, grams with grams, before you compare.
A 6-roll pack of toilet paper costs $4.59. Divide 4.59 by 6 and you get about $0.77 per roll. A 9-roll pack costs $7.29, which is about $0.81 per roll. The smaller pack wins, even though it looks like less.
Some things you buy once and use many times. A $60 jacket worn 30 times costs $2 per wear, while a $40 jacket worn 10 times costs $4 per wear. The dearer jacket is the better deal. And never trust bigger at sight: three 1-litre bottles at $2 each cost $6, which beats a 3-litre bottle at $6.50.
Most shelf labels print the unit price in small type in a corner, so read it before you grab. If you hold a coupon, subtract it from the price first. And watch the units: a quart of milk at $1.25 sounds cheap next to a gallon at $4.29, but four quarts make a gallon, so the quart route costs $5.00.
Divide price by amount in matching units, and the lower unit price wins.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.