How much would a fully done slant six cylinder head cost?

well lets see

100 bucks for valves
50 for springs
think it was 200 to mill .110 off
machine guides for positive lock seals and springs was 50
hardened seats and bronze guides 3 angle VJ 400
porting will be a big chunk 500+
new pushrods possibly 140 (get three extras!!)
new longer studs for the intake face was 50 bucks

just off the top of my head