95% of all active listings cost more than this number. It marks the very bottom fringe of the price range — only the cheapest 1 in 20 books are at or below it.

Use it as a floor check: pricing a book below P5 puts it in the cheapest 5% of the entire catalog.

1 in 4 books costs less than this. Also called the lower quartile — it marks the point where the cheapest quarter of the catalog ends.

Any book priced below P25 is in the bottom 25%. Combined with P75, it defines the price band where the majority of "typical" books live.

Exactly half the books are priced below this, half above. The median is the most honest single-number summary of the catalog's price level.

Unlike the average, a few extremely expensive books can't pull the median up. This is why the median is so much lower than the mean — rare high-priced books skew the average upward but leave the median untouched.

3 in 4 books cost less than this. It marks the top of the "normal" price range — only the most expensive quarter of the catalog sits above it.

If you're pricing a book above P75, you're in premium territory by catalog standards. P75 − P25 gives you the IQR, the spread of everyday pricing.

Only 1 in 20 books costs more than this. This is where premium, rare, and collectible books live — the upper edge of the realistic price range.

Anything well above P95 is exceptional and likely a rare collectible, a pricing error, or an imported item. Use it to spot true outliers quickly.

The plain average divided by the median. Any value above 1× means expensive books are pulling the average above the typical price. The further above 1×, the more the mean is misleading as a "typical" price.

A ratio of 3× means the average price is roughly 3× what a typical book actually costs. Always read both: the median tells you what most books cost; the mean tells you how much rare expensive listings inflate the picture.