open the cost_mod.lua with notepad++ and change the line 19 to your directory.
for me it was from
C:/Program Files (x86)/Steam/steamapps/common/Train Fever/res/
to
H:/SteamLibrary/SteamApps/common/Train Fever/res/
and maybe you need to create the file costs.lua in the config folder.
it has installed, but crashes the game when i try to start a new game…
