Many times, I get an economy going that is making tons of credits. After a while, I have spent all I can find to spend, am already putting out one ship or improvement per turn when I want to, and my treasury just fills up. Sometimes I pay incredible cash amounts for techs I don't really need. Boring. I have tried buying starbases, but they don't do that as much anymore. AI is getting too darn smart, I tell you. What is a poor little spendthrift to do?
I remember Asteroid Mines used to have upgrades. I would like upgrades to this generation of Asteroid Mines. 500 cred gets me one production point. 5000 cred should get me a second production point. If that doesn't drain my pockets, 50000 for the third point should do it. 
There, we have two levels of upgrade for Asteroid Mines again!