Price spread index: how much the same product varies between shops

What the numbers say

• The median spread is 29.9% but the mean is 62.4% — a heavily right-skewed distribution. A small share of products differ wildly and drag the average far above what a typical shopper encounters.
• 62% of products (7,805 of them) vary by 20% or more between the cheapest and dearest shop. These are not promotions — this is the price difference for the same article at the same moment.
• Only 14% of products (1,751) are priced within 5% everywhere. The assumption that the market prices itself into line is not supported by the data.
• At the 90th percentile the spread reaches 135.4% — meaning for one product in ten, the most expensive offer is more than double the cheapest.
• 70.4% of listings are in stock. The rest stay published at a price you cannot actually buy, which is why price should never be read without availability.

Spread by brand

Brands with enough multi-shop products for a median to mean something. Median low price is the cheapest offer for a typical product of that brand.

Method, and what this is not

• Products are identified by EAN barcode. Only products found in at least two distinct domains, with a price collected in the last 45 days, are compared.
• Grouping is by domain, not by shop record. The same shop can exist in several customer accounts; counting records rather than domains would make one shop look like five and drive the measured spread artificially to zero.
• 25 groups were discarded because the dearest offer exceeded the cheapest by more than 10×. That almost always means a barcode shared across pack sizes, not a real bargain.
• Brands whose median spread exceeds 150% are withheld. At that level the barcode grouping is untrustworthy for the brand rather than the market being genuinely that volatile.
• This is not a representative sample of e-commerce. Coverage reflects the shops this infrastructure observes — weighted towards perfumery, cosmetics, toys and household goods. Do not read it as national statistics.
• Figures are aggregate by construction. No individual shop's prices are published, and nothing about who monitors whom is disclosed.