I didn't build those 75 economic bases just for trade. I was actually trying to see if I could get a score over 400,000 for a metaverse game, and so I built 250 economic starbases to try to boost my production and research.
Wow, that's a lot of starbases. But I can understand. I too build many starbases as well to boost both production and research. Using them to increase trade is secondary since trade plays a very tiny role in my overall economy.
My games usually take a very long time to complete since I play in a huge galaxy and I build lots of very expensive capital ships that are very time consuming to build. For example, if I were to rush the production of a single dreadnought to be built in one year it would cost over 42,000 BC to build. Having multiple economic starbases can help reduce the amount of time it takes to build very expensive capital ships. It still takes a long time to build these ship, but it take even longer without the boost from economic starbases.
The most economic starbases I ever built is probably about 135 that are fully decked out defensively and offensively. I figure I use 35 Constructors to build each of my economic starbases, that means I built 4,735 constructors to build all these bases. That excludes influence, military, and resource starbases.
4,735+ Constructors in a single game sounds nuts, but one of my capital ship can easily outclass 8 capital ships from other races.