The book gives us stats on it's helmets. However, it seems to fail to give us an ingame price. Any help, erratta, anything?

seriously, no one?

They are not there and there has been no errata for them AFAIK.

does ffg ever get on these questions?

Well I am not FFG but I know the costs here ya go:

Circlet - 50 SC
Forehead Protector - 80 SC
Leather Hood - 40 SC
Casque - 1 GC
Mail Coif - 5 GC
Open Helm - 20 GC
Great Helm - 40 GC

I hope that helps.