[Agrajag]

I just have to play the role of annoying guy here, but the answer is: depends.
The gold and resource cost depends on what kind of nation you are playing, a nation with "advanced" technology would forge broadswords faster than a more "primitive" one, a broadsword wielder will cost more in a nation where there aren't many of him etc.

I'll try to think up a satisfactory formula though if that will make you happy =P.

How about this:
Multiply all of the positive traits and divide by the negative ones, then divide by 1,000,000 and voila! there's your gold cost!
Resource should depends on weapons, but I can't think of an idea right now...
Here is an "official" formula:
(Strength)*(Attack Skill)*(Defence Skill)*(Precision)*(Morale)*(HP)*(MR)*(Protection)/(Encumberance)=Gold Cost.
(If Precision is irrelevant, just treat it as 10 I guess).
With this formula a soldier with:
Strength 10
Attack 10
Defence 10
Precision 10
Morale 10
HP 10
MR 10
Protection 10
Encumberance 10
would gost 10GP.
You could also fiddle with the 1,000,000 bit to reflect how hard the soldier is to obtain.

Obviously, this is not the formula I use because I'm not actively modding, but it is a nice one...