Lintman:
I believe the Upkeep amount is so high as a play balance mechanism. Personally, I think its about right. Operating a fleet is a VERY expensive operation TODAY. Who knows what the future will bring.
That said, do you have problems in your games with resources? I always seem to have resources falling out my ears. I have custom data set in which I reduced the amount of resources that facilities produce AND I've upped the cost on many ship components and hulls. Even at that, I find that I am usually hovering around the 50k mark in all three resources.
I just rarely need to maintain a large fleet. The AI tends to be extremely passive and treaty happy. By the time it starts getting uppity, my Tech levels are so far ahead that I usually need very few ships to overpower them.
If the AI was more aggressive, it might force me to keep a larger fleet in being and thus slow my exponential growth. I am currently fiddling with the AI to accomplish just that.
Talenn