Ahhh ok, I edited some stuff in export_descr_unit.txt and fired up RTW. I know what you mean now, it had no effect.

Sorry, was my mistake.

Go into Data\world\maps\campaign

Assuming you're modding the merc costs for an Imperial Campaign, enter the imperial_campaign folder, open up -> descr_mercenaries.txt

This should be what you are looking for.

Note: The same mercenary in a different region could have different costs. Eg:

pool Thrace
regions Thrace Propontis Tribus_Getae Bithynia
unit merc peltast, exp 1 cost 550 replenish 0.125 - 0.25 max 1 initial 0
unit merc thracian, exp 1 cost 800 replenish 0.125 - 0.25 max 3 initial 1
unit merc bastarnae, exp 0 cost 1700 replenish 0.05 - 0.08 max 1 initial 0
unit merc greek hoplites, exp 0 cost 850 replenish 0.03 - 0.07 max 1 initial 0


pool Northern_Greece
regions Paionia Macedonia Thessalia
unit merc peltast, exp 0 cost 600 replenish 0.05 - 0.08 max 1 initial 0
unit merc illyrian, exp 0 cost 650 replenish 0.05 - 0.08 max 1 initial 0
unit merc thracian, exp 0 cost 800 replenish 0.05 - 0.08 max 1 initial 1
unit merc greek hoplites, exp 0 cost 850 replenish 0.05 - 0.08 max 1 initial 0

G'luck!