You walk past a display of Shine Muscat grapes and see a huge “¥199.”
“Whoa, cheap!”
Then you get closer.
“Per 100 g.”
And the excitement is over.
If the bunch weighs 500 g, the price is ¥995. At 600 g, it is ¥1,194. You can simply refuse to buy it once you see the total, so perhaps no harm is done. But that misses the irritating part: the display has already triggered the “cheap!” reaction. Even without a purchase, there is still a tiny sequence of “¥199! → wait, per 100 g → so it is actually over ¥1,000.”
Why does this pricing format exist? Was it invented to make expensive food look cheap, or did a sensible consumer-comparison tool become useful for marketing?
The second explanation is much closer to the evidence.
1. Unit pricing was originally designed to help shoppers
Unit pricing converts prices into a common measure: per 100 g, per kilogram, per 100 ml, and so on.
The purpose is straightforward.
If one package is 300 g for ¥900 and another is 450 g for ¥1,200, package prices alone do not make the better value instantly obvious. A common unit lets shoppers compare them.[1][3]
So a per-100-g price was originally supplementary information for comparison.
It was built as a consumer aid.
The trouble starts when the supplementary number begins dressing like the main price.
2. The modern history points to consumer protection, not a trick invented to look cheap
It is difficult to identify one universal “first” use of unit pricing. But the modern supermarket system has a well-documented history.
The U.S. National Institute of Standards and Technology says unit pricing expanded in the early 1970s during the truth-in-labeling era, when consumers demanded clearer information. The 1966 Fair Packaging and Labeling Act, the spread of supermarket checkout scanners in the early 1970s, and the need to compare different package sizes all formed part of that background.[1]
Tokyo also built a unit-pricing system in the 1970s. The ordinance framework was established in 1975, unit-pricing items were designated in March 1976, and implementation began in July 1976 with 60 designated items.[2]
So the ancestor of the “per 100 g” label was not “how can we fool shoppers?”
It was closer to “stop making shoppers do package-size arithmetic.”
3. Meat has an especially long history of per-100-g pricing in Japan
The familiar Japanese meat-counter label — for example, “domestic pork ¥198 per 100 g” — is not accidental.
Fair competition rules for meat labeling had been introduced progressively at the prefectural level since 1970 and were unified nationally in 1995.[4]
A Japan Fair Trade Commission report for fiscal 1989 described prefectural meat-labeling rules as requiring quantity and selling price to be shown, in principle, per 100 g.[5]
The current fair competition rules still use the 100-g unit as a core reference for meat pricing.[6]
So for meat, the answer to “why 100 g?” is quite rational.
Packages vary in weight, and shoppers need a common comparison unit.
So far, no villain is required.
4. Put the same format on Shine Muscat grapes and it suddenly feels like a trap
Many shoppers have decades of practice reading meat prices. They know that “¥198” at a meat counter usually does not mean “the whole tray costs ¥198.”
Fruit is different. People often encounter prices per bunch, bag, or piece.
If a sign first presents a giant “¥199” and only later reveals “per 100 g,” the brain can briefly activate a completely different pricing model:
“¥199 for the bunch?”
And most shoppers cannot look at a bunch of Shine Muscat grapes and instantly estimate its weight.
A common response is, “Obviously a bunch cannot cost only ¥199.” But what is obvious to produce staff is not necessarily obvious to every customer.
Customers should not need to memorize both the current market price and the expected weight of a bunch before they are qualified to read the sign.
Research on produce pricing also finds that whether an item is normally priced per piece or per weight affects consumer evaluations, while providing weight information improves comparison and confidence.[8]
5. Research really does find that the smaller unit can make the same price feel cheaper
This is the most interesting part.
A 2019 experimental study compared equivalent prices expressed with different measurement units.[7]
For example:
¥199 per 100 g
and
¥1,990 per kg
describe exactly the same unit cost.
Across four studies, prices expressed with the larger unit, such as per kilogram, were perceived as more expensive than prices expressed with the smaller unit, such as per 100 g. Those price perceptions then affected purchase intentions.
In other words, a smaller measurement unit can make the same real price feel cheaper.
The researchers call this a measurement-unit effect.
Crucially, the effect became weaker when shoppers were shown both the unit price and the actual retail price.[7]
So these two displays are not psychologically equivalent:
“¥199 per 100 g”
and
“This bunch ¥1,194 — 600 g — ¥199 per 100 g.”
The second one asks much less work from the shopper.
6. So is per-100-g pricing a marketing tactic?
The answer has two layers.
The system itself was created to make comparison easier.
But the choice of unit, the size of the number, the visual hierarchy, and whether the actual total price is equally prominent can change how cheap or expensive the product feels.
The 2019 study explicitly discusses measurement-unit choice as a strategic option in price presentation for retailers.[7]
So saying,
“Every per-100-g label is designed to deceive”
goes too far.
But saying,
“Making the smaller per-100-g number the most visually prominent has no effect on perceived cheapness”
is also wrong.
The effect has been demonstrated experimentally.
What cannot be inferred from a sign alone is the intention of a particular retailer. A store may be following a standard system, an industry convention, a comparison format, or a merchandising template rather than deliberately exploiting the effect.
We may not know the intent.
We do know the effect.
That distinction matters.
7. “If the total is too high, I just will not buy it” does not remove the annoyance
Yes, if you see the final price and put the item back, your wallet is intact.
But the shopping experience still contains a cost.
You see ¥199.
You react: “Cheap!”
You inspect the product.
You notice “per 100 g.”
You check the weight.
You multiply.
“Oh. Over ¥1,000.”
You put it back.
¥199 brought you in. ¥1,194 brought reality with it.
The display may not have converted into a sale, but it already captured attention and created an expectation.
That is why “you did not buy it, so what is the problem?” misses the point.
The irritating part is not only losing money.
It is repeatedly being made to run the script “cheap! → wait, no.”
8. “A bunch obviously cannot be ¥199” is knowledge for staff, not a duty for shoppers
Produce staff may know the day’s market, typical bunch weights, and that ¥199 for an entire premium bunch would be implausible.
The customer is not taking a produce-department certification exam.
Even someone who understands meat pricing may have no idea how many grams a particular bunch of grapes weighs.
The point of a price display should not be “people with enough category knowledge will eventually decode it.”
It should let an ordinary shopper understand the transaction without unnecessary guessing.
That is especially ironic because unit pricing was originally designed to reduce exactly that kind of mental arithmetic.
9. A per-100-g label is not automatically illegal
Accurately displaying a price per 100 g is not inherently an unlawful practice.
For some categories, including meat, unit pricing is deeply embedded in formal labeling rules.[6]
At the same time, Japan’s Act against Unjustifiable Premiums and Misleading Representations restricts price and transaction-condition displays that make an offer appear significantly more advantageous than it really is and may improperly attract consumers.[9][10]
That does not mean “small text saying per 100 g = illegal.”
Whether a particular sign crosses a legal line depends on the overall presentation: type size, placement, whether the actual retail price is visible, the product format, and the surrounding information.
So two questions should stay separate.
“Is this display annoying and easy to misread?”
and
“Is this display legally unlawful?”
The first can easily be true without automatically proving the second.
10. The clearest design is simple: make the total price primary and the unit price comparative
There is no need to abolish unit pricing.
It is useful. Keep it.
Just give the numbers the right jobs.
For a 600-g bunch:
This bunch: ¥1,194
600 g
¥199 per 100 g
Now the shopper can immediately see both “what will I pay?” and “is this good value compared with the next item?”
If an item is genuinely sold by variable weight and the final total is not yet known, a realistic example — “500 g would cost about ¥995” — can reduce the need for shoppers to guess the weight and do mental multiplication.
Comparable products should use consistent units. When an actual package total exists, that total should not be visually treated as an afterthought.
That is much closer to the original purpose of unit pricing.[1][3]
The conclusion is simple:
Do not remove the per-100-g price. Do not let it cosplay as the total price.
Unit pricing is a comparison tool.
The moment it starts looking like the product’s full price, it can take your “Whoa, cheap!” reaction before the real total arrives.
And even if you never buy the grapes, the final reaction is still:
“Could you have just shown me ¥1,194 first?”
