Mine was an anomaly at 10 USD (they literally didn't know anything about cameras). It seems like on that one auction site a Nikkormat body in great shape can break 80 or 90 USD, minor issues around 60 USD and major issues (eg, meter erratic, battery corroded shut, et cet) would be about 30-40 USD. Forgive me, the exchange rate to BPS (?) must have changed since I last knew what it was.
As far as the Nikkorex F goes it's a little less technically impressive but a collector who wants a complete set of Nikon bodies might feel a dinged up Nikkormat to be a fair trade, especially if like many collectors they have several Nikkormat bodies of each type. As far as I know the Nikkorex F goes for about 60 USD in body only sales.