Collections are quoted by their floor price as though it were a share price. It is the cheapest item currently offered for sale, which is a very different quantity with very different behaviour.
The floor is one seller's asking price
A floor is the lowest active listing across a collection at a given moment. It is an offer, not a completed transaction.
One holder deciding to sell quickly moves the number for everyone, even though nothing has changed about the collection or about anyone else's holding.
Listings can also be withdrawn at any time, so the figure can rise simply because someone cancelled rather than because anyone bought.
Items within a collection are not interchangeable
Non-fungible tokens differ in traits, and prices within a single collection can span orders of magnitude between common and scarce items.
The floor by definition describes the least desirable item on offer, so applying it to the whole collection values scarce pieces at the price of common ones.
Multiplying the floor by total supply produces a headline capitalisation that overstates the cheap end and understates the expensive one simultaneously.
Depth beneath the floor is what matters
A floor supported by a single listing is fragile, because one sale removes it and the next listing may sit far higher or far lower.
What indicates a real price level is the number of items listed close to the floor and the standing offers waiting beneath it.
Those bids are the prices someone will actually pay, which is a stronger measure than the price someone hopes to receive.
The number is straightforward to manipulate
A holder can buy their own item at an inflated price using a second wallet, producing a sale record that costs only fees.
Listing and delisting patterns can be used to keep a floor artificially high, since removing cheap listings raises the quoted figure without any purchase occurring.
Thin collections are especially exposed, because a small number of coordinated actions can control what the market sees.
Better readings come from transactions
Completed sales over a period, separated by trait rarity, describe what buyers actually paid rather than what sellers requested.
The count of unique buyers is informative too, since volume concentrated among a few addresses says something different from the same volume spread widely.
None of these are as convenient as a single number, which is precisely why the floor continues to be quoted despite describing so little.