Before pricing anything in this category, do the check that decides whether it can be sold at all.
The check that comes first
Recall status, and whether anything safety-critical is missing. Recalled goods and items with a safety part missing may not be sold here — that is Metzee policy, not advice. Prohibited items.
An item failing that check is not a cheaper item. It is one with no price here.
Then what moves the number
Completeness — straps, fixings, inserts, rain covers, the manual.
Condition and cleanliness, said honestly.
Age of the item, read off the date stamp rather than estimated.
Brand, which in this category does carry weight.
For safety items, how much of the history you can confirm.
Why two of the same differ
One seller gave the model number, the date stamp and the full parts list, so a buyer could look up the recall themselves. The other said "barely used". Describing baby items.
How to find out rather than guess
Compare completed sales of the same model in the same completeness, and remember that most of this category is nearly-new because it was outgrown rather than worn out — so condition separates less, and completeness separates more.
Clothing and toys
Worth far more as lots by size than individually. One size, washed, described, counted.
Questions people ask
Are car seats worth selling?
Where not recalled, not expired, complete and you can speak to the history. Otherwise no.
Does a brand name raise the price?
More here than in most categories, because parents search by it.
Is a missing manual a problem?
Say so and link the manufacturer's. For anything that must be installed correctly it matters.
More: pricing baby items, selling them.