I'm playing on tough, I have a patch, whether thats 1.1 i'm not sure, i'll have to check.  I can buy a mining station for 6000 if it's only the first level.  When it's been upgraded it costs me much more.  Though, beaware that I always go for the diplomatic upgrades, and went for full Demplomacy as my starting stats, and build the galactic wonders for it so I always have a massive diplomatic advantage.  I think my starting Deplomacy was an 80% bonus.  I try to buy the stations as early in the game as possibly, as later on I found that in my other game the Drengi were a pain to buy off.  Think I ended up spending over 100 to get 3 bases.  Though my treasury is at 2 million so I can afford what ever price they want, and I'm more than willing to give it too them.  Most of my starbases arn't upgraded to the max, and quite a few are at the lowest upgrade level.  Hope that helps.  Price of the starbases though isn't really a problem.  If they want to charge me 1 million for all their bases, they can have it lol.  

Tell me more about this fleet, I have (for the first time) a good ethical allignment, what are these weapons you speak of?  Also, my military at the moment is an exspenditure of 947 BC.  I have an income of 22623 so thats pretty small but I manage to have a much more powerful military with a lower exspenditure than the other races.  Whats your might rating like (rank would be useful).  I like to keep a good rating so people won't attack me.  Also, how many ships do you have? 
I'm looking into the idea of a very small but very effective fleet.  Oh and another thing, is there any way to tell what bonuses planets have, as the only way I know at the moment is by writing it down when it tells me, but there's going to be better worlds which I conquer with higher starship bonuses but at the moment, I don't know what worlds they are?
Cheers