Hello, what I'm about to explain works with all the three Alien Breed games.
I have the GOG version, but the folder should be the same for the Steam version.

1) go in Documents\My games\UnrealEngine3\AlienBreed2AssaultGame\Config\
2) open the file AlienBreed2AssaultGame.ini with a text editor
3) find the lines
[ExampleGame.ABItem_CashPickup]
CashPickupAmount=200
4) change the number 200 to whatever you want and then save the file.
5) enjoy.