I think I�ll buy your argument regarding base item resource cost.
R=Base cost*(Construction level+Blood/10)
Possibly Construction level^Z though. It should be really hard to mass produce the higher level items.
Z=1.2 maybe
Proposed resource cost:
R=Base cost*(Construction level^1.2+Blood/10)
A Hellsword would then cost:
R=6*(6^1.2+1)=57.51=58(rounded)
Sword of swiftness:
R=4*(4^1.2)=21.11=21(rounded)
Robe of Invulnerability:
R=1*(6^1.2)=8.58=9(rounded) (Assuming minimal resource cost of 1)

*****y board rules wouldnt let me use "more than" or "less than" signs
Edit: With the current proposal a Robe of Invulnerability would cost:
4*80*1.25=400 gold
[ March 01, 2004, 16:14: Message edited by: Bossemanden ]