Edit GP Rain damage

There's one other relevant bit. The code Madsiur posted has

Code:

BNE $3FE9   (branch if there was actually some GP to throw)

Here's the code that jumps to:

Code:

C2/3FE9: A2 02        LDX #$02
C2/3FEB: 86 E8        STX $E8
C2/3FED: 20 B7 47     JSR $47B7      (24-bit $E8 = A * 2)
C2/3FF0: A5 E8        LDA $E8        (A = gold to consume * 2)
C2/3FF2: AE C9 3E     LDX $3EC9      (Number of targets)
C2/3FF5: 20 92 47     JSR $4792      (A / number of targets)
C2/3FF8: 8D B0 11     STA $11B0      (Sets maximum damage)
C2/3FFB: 60           RTS

GP Rain does a total 2 damage per GP thrown, divided equally among the targets. If you want to change the 2x multiplier instead of/in addition to the cost, C2/3FE9 is the place to do it.