A seller's stated value is not what the item is worth

A stated value is a catalogue price. Nobody is obliged to pay it, the seller least of all — and where the seller offers to buy the item back, the rate it offers is usually a fraction of the value it printed.

So this site carries the two figures in separate columns and never averages one in place of the other. The seller's arithmetic is reported because it is what the marketing claims; the arithmetic from observed prices is reported because it is what a buyer can act on. Publishing only the first would restate a claim as a finding.

Then the terms apply. A sell-back at 70% takes 30% of whatever is left, and a delivery charge takes a flat amount off every purchase that ships. A box whose stated average is $180 and whose observed average is $95 realises $66.50 at a 70% sell-back — against a price of $100.

Where an outcome carries a probability but no price anyone outside the seller has recorded, no figure from observed values is published at all. Falling back on the stated value there would quietly reintroduce exactly the number the column exists to avoid.