It would be great if people could share their formula for costs.

I remember WesW saying he constructed one for his MTW MedMod when it was just in its infancy. But I never saw it and get the impression RTW modders often rely more on judgment than mechanical formula.

CA does not seem to cost things according to their effectiveness - the SP upkeep is based on assumptions about troop types, rather than stats. And even the purchase costs, which you would think should be based on stats to balance MP, don't always seem to be justifiable on those grounds.