You can use Cheat Engine OR what i prefer and what i think is way better and has better searching options Art Money you can get the full version on TPB
There are many utilities which dump into a file - here is one: http://ntsecurity.nu/toolbox/pmdump/
Game cheat can probably do it too, artmoney can also do that http://www.artmoney.ru/
However you will have to identify the pattern around your value on your own (if there is even a pattern around it - if not tough luck) after you identify the pattern you will have to write the code that scans all of the memory for that process looking for the pattern.
There are 2 gameconfig files:
...\steamapps\common\Xenonauts\assets\gameconfig.xml
...\steamapps\common\Xenonauts\assets\mods\xce\gameconfig.xml
If nothing else works you could edit the money directly in memory while you play. There are tons of utilities out there, like ArtMoney (I haven't tried it).
Be very careful, some of these utilities could get you VAC banned, and you don't want that.
I remember trying to do something similar with MechWarrior: Online - I wanted to be able to display the real-time game map in a separate window. I got as far as a PoC that printed out co-ordinates. What I did was used ArtMoney to track down some memory locations containing the (X,Y,Z) values - this only works if you KNOW the values, so you can search for them, luckily at the time MW:O allowed you to display your co-ordinates and heading on screen for debugging.
The main problem was that, as pointed out by other commenters, a) this could trigger anti-cheat warnings and b) you'd have to update your software for each new release of the game.
Anyway, here's my code in case it is of use to you - sorry it's probably not very self-documenting: https://www.dropbox.com/s/0r1lywcctxitrcu/proofOfConcept.cpp?dl=0
https://www.dropbox.com/s/hhjwpzqtraouulr/proofOfConcept.h?dl=0
This is problematic for any game that doesn't have plugin or mod support - how are you going to obtain co-ordinate data? However, it can be done if you can spy on the game process's memory, and find the X, Y, Z variables, possibly using something like http://www.artmoney.ru/ (Note that certain DRM or anti-cheating schemes will make this more difficult.)
I remember doing something similar for Mech Warrior: Online - I was thinking of making a 3rd-party application which needed real-time data on the position of the player in the game map. MW:O had a debug mode which showed you your XYZ co-ordinates, so I was able to use ArtMoney to search the memory for those values. Once I'd found a data structure and reverse-engineered (some of) its fields, I also found a pointer in a fixed location to that data structure.
I never actually built the application I was planning, but here's the proof-of-concept code I wrote: https://www.dropbox.com/sh/llhqtjg0x6bc2xu/AAAjP4IL4kDB0LrwQPXoiugJa?dl=0
Of course, if you have mod-tools, none of that would be necessary. So while you might have to employ memory-spying for E:D, I would imagine for GTA you could just write a mod which outputs the co-ordinates to some shared memory location or TCP port or something.