Unit price
Unit price is what a sale or listing paid per sat of its category: the price less the output's own value, divided by the category's sats it holds.
The formula
Rare sats travel inside outputs that are worth sats of their own, and the buyer gets that value back with the output. So the site prices the premium, not the price:
unit price = (price − the output's value) ÷ the category's sats it holds
to the hundredth of a sat. A block 9 chunk of 6,280 sats, in an output of 6,280 sats, listed at 94,200 sats, has a unit price of (94,200 − 6,280) ÷ 6,280 = 14 sats per sat. A single alpha uncommon in a 546-sat output sold for 45,546 sats has a unit price of 45,000.
Listings and sales use the same measure, so they compare directly. A category's floor is the lowest unit price among its active listings. A sale is of one category, its own (see bundles), and a sale that splits sats out of an output counts only the sats it sold.
Which price
A sale's price is the marketplace's, found on chain: on some marketplaces the listing price, which includes the marketplace's seller fee, elsewhere the seller's payment plus the marketplace fees in the transaction. On raresats.net the price is what the seller receives; the buyer's 2.5% fee is on top and not part of it. A sale whose transaction carries no marketplace fee output the index knows is marked Unknown, and its price is the seller's payment.
A sale for no more than the output's own value paid nothing for its sats: it has no unit price above zero, and it is in the table but not on the chart.
The median line and outliers
A category's line is the median unit price of its counted sales over the 30 days up to each sale. A sale is an outlier when its unit price is more than 10 times, or less than a tenth of, the median of the category's previous 7 sales within a year (at least 5 of them, compared by ratio). When the year its lead sat was mined has 5 such sales of its own, it is judged against those instead, since a 2009 alpha uncommon, for one, sells at a price tier of its own. Outliers are drawn hollow and left out of the line and the market numbers. Inscribed sales are left out too, and pending sales count only once mined.