You'll find this chunk in the XComPGRetrofit.INI
It controls the costs for the retrofit.

Default costs are as follows
The costs reflect the difference in price between the current weapon and the weapon you are upgrading to, plus a 'retrofit tax' that scales with tier.

The retrofit tax is meant to offset the difference between selling the old weapon on the black market or retrofitting it. Retrofits are meant to be just a little more expensive and time consuming than selling the old gear and building new gear, but still reflects a discount for trade-ins.


; ===== RIFLES =====
LaserToMag_Rifle_Supply=15
LaserToMag_Rifle_Alloy=1
LaserToMag_Rifle_Dust=1
LaserToMag_Rifle_Core=0

MagToCoil_Rifle_Supply=20
MagToCoil_Rifle_Alloy=1
MagToCoil_Rifle_Dust=3
MagToCoil_Rifle_Core=0

CoilToPlasma_Rifle_Supply=25
CoilToPlasma_Rifle_Alloy=1
CoilToPlasma_Rifle_Dust=1
CoilToPlasma_Rifle_Core=1

; ===== SNIPERS =====
LaserToMag_Sniper_Supply=15
LaserToMag_Sniper_Alloy=1
LaserToMag_Sniper_Dust=1
LaserToMag_Sniper_Core=0

MagToCoil_Sniper_Supply=30
MagToCoil_Sniper_Alloy=1
MagToCoil_Sniper_Dust=3
MagToCoil_Sniper_Core=0

CoilToPlasma_Sniper_Supply=25
CoilToPlasma_Sniper_Alloy=1
CoilToPlasma_Sniper_Dust=1
CoilToPlasma_Sniper_Core=1

; ===== SHOTGUNS =====
LaserToMag_Shotgun_Supply=15
LaserToMag_Shotgun_Alloy=1
LaserToMag_Shotgun_Dust=1
LaserToMag_Shotgun_Core=0

MagToCoil_Shotgun_Supply=30
MagToCoil_Shotgun_Alloy=1
MagToCoil_Shotgun_Dust=3
MagToCoil_Shotgun_Core=0

CoilToPlasma_Shotgun_Supply=25
CoilToPlasma_Shotgun_Alloy=1
CoilToPlasma_Shotgun_Dust=1
CoilToPlasma_Shotgun_Core=1

; ===== CANNONS =====
LaserToMag_Cannon_Supply=15
LaserToMag_Cannon_Alloy=1
LaserToMag_Cannon_Dust=1
LaserToMag_Cannon_Core=0

MagToCoil_Cannon_Supply=30
MagToCoil_Cannon_Alloy=1
MagToCoil_Cannon_Dust=3
MagToCoil_Cannon_Core=0

CoilToPlasma_Cannon_Supply=25
CoilToPlasma_Cannon_Alloy=1
CoilToPlasma_Cannon_Dust=1
CoilToPlasma_Cannon_Core=1

; ===== ARMOR =====
PredatorToWarden_Supply=55
PredatorToWarden_Alloy=5
PredatorToWarden_Dust=10
PredatorToWarden_Core=0

PredatorToSpider_Supply=25
PredatorToSpider_Alloy=1
PredatorToSpider_Dust=1
PredatorToSpider_Core=0

PredatorToExo_Supply=35
PredatorToExo_Alloy=1
PredatorToExo_Dust=1
PredatorToExo_Core=0

ExoToWar_Supply=45
ExoToWar_Alloy=4
ExoToWar_Dust=10
ExoToWar_Core=1

SpiderToWraith_Supply=55
SpiderToWraith_Alloy=4
SpiderToWraith_Dust=15
SpiderToWraith_Core=1