Why is there a price floor for a given build?

Why

• The floor is arithmetic rather than opinion. Material, hardware, assembly, packaging, freight and the platform fee are all per-unit costs, and each has a lowest plausible figure that this desk records and dates. Adding them produces a band below which a listing can only be selling a different build, absorbing a loss, or planning a substitution after payment has already cleared.
• Above the floor, price stops predicting quality. Two listings at the same figure can differ in material and hardware, and a listing well above the floor can still ship the cheaper build, because nothing in the transaction ties the price to a written specification. That is why the floor is used to reject implausible listings rather than to rank plausible ones, and why it never appears as a quality score. The floor answers one question only, which is whether a listing is plausible at all. It cannot rank two plausible listings against each other, and using it that way produces confident conclusions from arithmetic that was never designed to support them.
• Freight moves the floor further than any component does. The same item sent by economy service and by express differs by more than most material changes cost, so a comparison that ignores the carriage line and the quantity tier is comparing two different transactions. The landed-cost waterfall is where the two are made comparable, because it puts every line on one page in a fixed order.
• The floor shifts with the batch rather than with the season. When a component is substituted the floor moves, and a listing that sat above it last year can sit below it this year at an unchanged price. Recording the figure and the date when a build was first seen is what makes that movement visible later, which is why comparison notes on this site are dated rather than remembered. A price without a date cannot show movement, and a floor without a date cannot be re-checked when a component changes. The date is the part of the note that keeps the rest of it usable a year later.

When this answer flips

• The listing is selling a single unit from overrun stock, because clearance pricing can sit under the floor without any component having changed.
• The quantity tier changes, because the per-unit floor for a bundle of five or ten is genuinely lower than for one, and comparing a bundle price against a single-unit floor is an error.
• The freight line is left out of the comparison, because a low item price with a high carriage charge can sit above the floor once the two are added together.

Three things to do next

1. Build the full landed cost
2. Read the seller rating question
3. Compare the edge paint and corner construction