One of the things I think happens with Econ being unbalanced is: Game Pacing.
I am pretty sure that game pacing has no effect on maintenance / costs to rush. This means that there will be a huge devaluation of credits in maps with Fast / Very Fast research / pacing settings. The game will end or at least be 'determined' by turn ~75.
However, if you were playing a very slow map, credits would mean much more. It may take twice as long to get to the deterministic win position (say 150 turns to know you can dominate the rest of the game). This might not be quite the same if you are doing an influence win since I'm pretty sure influence growth isn't determined by pacing, but you get the idea. In a normal to very slow map, maintenance costs are much more significant.
At the very least, I think they should have maintenance, rush buy, and influence all scale with game pacing / research. I would also be interested in something like inflation - costs go up as the game goes on for maintenance at least (again making credits slightly more useful). Likewise, they could just make credits more useful like being able to rush research, and/or lower the cost to rush ships and structures.