As commented in your last suggestion, the sale immediately after yours won't be usable because trades are often made between the 2 users at deficits to be made up later, so there's unreliability in valuing an individual exchange at face value.

Unless something's being missed, your purchase values the Herald's Helm at almost 0 Keys, so that needs to be excluded and can't really be considered counter-evidence to require a third sale for an outlier determination.

https://backpack.tf/profiles/76561198122976167#!/compare/1783382400/1783468800

Well-Worn variants of the Minigun, albeit not Pro KS ones, are listed for <30 Keys, and there's a seller for the Capotain at 37 Keys

https://backpack.tf/classifieds?item=Minigun&quality=5&tradable=1&craftable=1&texture_name=Team+Serviced&wear=Battle+Scarred&particle=701&australium=-1

https://imgur.com/a/tTkexdX

https://archivist.tf/history?item=Neutron+Star+Pure+Tin+Capotain&at=2026-08-25&range=3